You bought that mountain bike with dreams of tackling South Mountain or the Phoenix Mountains Preserve, but then you discovered something ? mountain biking can be a lot harder than pushing the old steed down a sidewalk. Perhaps you'll be in shape someday to grind up gravel-ridden slopes and rocket down luge-run trails like the big boys and girls. In the meantime, there's Papago Park. Go ahead, pump up the tires and clean the cobwebs out of the spokes. Papago Park is centrally located and won't cost you a cent to enjoy. Most of the trails are gentle up-and-downs that will only trouble the klutziest of children or adults. If you can ride a bike, you can probably mountain bike at Papago. Yet for all its friendliness to novices, it offers many of the same pleasures as any other mountain bike ride ? gorgeous views of rising crags, quietude, and the occasional glimpse of wildlife, mostly coyotes, lizards or rabbits. The best place to access Papago for bike riding is off Galvin Parkway. Instead of going east to the Phoenix Zoo, take the entrance road just opposite into a parking area. Trails from there run all over the park, and it's not easy to get lost. Better hurry out there, though ? civic leaders have grand designs to develop the park in the future, and the long series of interconnected trails that are great for biking someday could be blocked by a hotel or retail shops. For now, your path to biking fun awaits.