Located 54 km northeast of San Jose, the Parque Nacional Volcán Irazú area has few options in the park for mountain biking, but there are several great rides starting at the park.
First, the most popular ride it the down hill route back to Cartago. The summit is at 11,000 feet, so there is quite a descent over 30km back to Cartago.
Second, just before the ranger station gate, there is a rough dirt road on the right heading northeast. This road wraps around the back of the volcano descending for several kilometers. It is a very scenic and lush.
Third, about 2km south of the ranger station gate, there is a dirt road on the left heading east. This dirt road descends for 10km over to the base of Turrialba Volcano. It is also a very scenic ride through lush forest and pastures.
For the best experience, make sure to arrive on a weekday, the earlier the better. Try to arrive at the summit by 10am. The Information Center opens at 8am.
To reach the trailhead from San Jose, head east on Avenue 10 (unsigned) to the east side of town. Just past Calle 43 (unsigned), turn right heading south on RUTA 39 for about 1km. At the Rotonda Garantias Sociales traffic circle, head east on RUTA 215 towards Cartago. This route follows city streets to the beginning of InterAmerican Highway RUTA 2. Closely follow signs to Cartago as the route makes several turns. After about 10km, the route to Cartago abruptly turns right for 4 blocks. When this road ends, turn left for two blocks. Then turn right for one block to the start of RUTA 2 (as of April 2007, there was no signs for Cartago or RUTA 2 at the start of the highway). At the start of the Highway, turn left on to the major divided highway and proceed through the toll booth. Continue east on RUTA 2 for another 12km towards Cartago following the signs and generally staying in the left lane. The highway ends about 3km before Cartago onto a city street, Avenue 2 (unsigned). Continue east on Avenue 2 (unsigned) towards downtown Cartago. The route passes several plazas. On the east side of downtown Cartago, just before the end of Avenue 2 at Calle 14 (unsigned), there is the most scenic plaza, Plaza de la Bassilica. Behind the church is Calle 18 (unsigned). Turn left on Calle 18 for one block. At the intersection, veer right on a 45 degree angle heading northeast on RUTA 8 (unsigned). For the next 6km, generally follow the biggest road at intersections or veer right when in doubt. At 6km from the plaza, you will reach the intersection of RUTA 219 and RUTA 230 (signed).
At this intersection, veer left on RUTA 219 (the yellow roadside mileage markers indicate RUTA 8). Continue climbing north on this winding paved route to a distance of 30km from the Cartago plaza to reach the gate of the Parque Nacional Volcan Irazu. There is a small dirt road to the right just before the gate that is worth exploring. Beyond the gate, the crater rim parking area is a1km ahead next to the Visitor Center. Overall, it is 53km from San Jose and takes about 2 hours. It is 31km from Cartago and takes about an hour.
To reach the trailhead from Turrialba Volcano on the shortcut 4WD dirt road, follow the road to the Lodge. Continue past the lodge through the small town of Esperanza. Generally stay right at the intersections climbing up to RUTA 8. Turn right on paved RUTA 8 for 2km to the Irazu Ranger station.
Here are some basic notes on driving in Costa Rica for the tourist. There is a myth about the quality of the roads and of VW bus sized pot-holes. This may have been true years ago, but on the main routes, this is no longer true. With that said, there are still numerous challenges for first time drivers in Costa Rica. First, do not expect much out of so-call “highways”, like the InterAmerican Highway. The fancy name makes the uninitiated think this is a major 4 lane divided, restricted access road. Well, yes, about 1% is. The rest is two lane (marginally), undivided, rural roads with tons of traffic constantly stopping, turning, passing or driving slowly. Like every other road in the country, you can expect to see on the road numerous unexpected cows, cyclists, pedestrians, bus stops, school crossing zones, dogs, mud slides, police check points, unannounced one-lane bridges, missing manhole covers, and, of course, a never ending stream of semi-trucks driving erratically fast. What you do not find on any roads is much signage. There are infrequent signs indicating the distance to the next town, and even more infrequent are road names or numbers (if at all), including even within major towns. To make matters worse, signs that used to exist are disappearing due to deterioration or theft. Also, do not expect drivers to use their head lights, even in a heavy rain shower, unless it is really dark. This makes passing in rain a game of roulette since you can't see the oncoming traffic. Speaking of dark, do not drive at night since the roads in some areas can be ruled by those under the influence of alcohol.
If you have to drive through San Jose, make sure to do it at dawn to avoid the horrendous traffic all day long, including weekends. Keep in mind several maps show highways passing through San Jose. This is not true. They end abruptly on the outskirts of town and you have to slug it out in a crazy stop-and-go traffic and many unmarked turns to get to the other side all day long. There are unsigned so-called by-pass routes around San Jose, but finding them can be a challenging game of trial-and-error, and they are only marginally better.
If you have to drive on the Nicoya Peninsula, you can expect to find generally better roads with better signage. However, there are numerous unmarked eroded road sides, especially over stream culverts. do not drive at night. Watch out for the iguanas sprinting across the road.
A GPS unit can be helpful when navigating roads, however, the maps in Costa Rica were created using a special map datum. This datum is not usually available on GPS units but the road base maps were created with it. Therefore if you use the default WGS84 datum with a base road map on the GPS unit, you will always show a position being about 0.5 miles to the north of the road base map.
When picking up a rental car, make sure to check all the tires for wear, check the spare tire pressure, check the tire jack, and make sure to test the lock on the spare tire. It would be wise to quickly purchase a can of Fix-A-Flat.
Overall, Irazu Volcano National Park is the 3rd most popular mountain bike trail of all 16 mountain biking rides in Costa Rica.