The riding
Local operators offer cycling trips through the rural landscapes around Arenal. Check the route surface, amount of singletrack and technical difficulty before booking if your priority is mountain biking rather than a general sightseeing ride.
The area
La Fortuna is the base for cycling trips around Arenal. Match your stay to the operator's pickup arrangements and ask about the route surface and technical riding, since local cycling tours do not all offer the same MTB experience.