Another recommendation for Lavatrax, they´ll rent you a proper bike.
I got a Marin Wolf Ridge when I was there, stuck my own pedals on and it was lovely. The trails are spectacular.
Piceswise, flights are cheap.
Accomodation is about 45€ per night in a decent villa with breakfast.
Guiding 50€ per day
Bike Hire 30/45€ per day
Food is cheap, so is the beer and wine.
We rented a car for 100€ for 7 days.
There´s a massive difference between the north and south of the island. All the best trails are in the north but the nicest weather is south. Hence, we stayed in El Medano fishing village on the southern coast and used the rental car to get about.