Rich definitely go for it. PQ trail is a nice place to start. There are two entry points, one near Black Mountain Canyon park near the horse stables and another down at the bottom of the canyon kind of near the base of Qualcomm Hill. Basically it is the Sorrento Valley exit off of the 5 but it is hard to explain on the blog but easy to find with a map. Not so sure about renting bikes but yeah try Performance. If you do end up doing it more DO NOT go buy a new bike. Used mountain bikes are the easiest thing to find on craigslist. Make sure you talk to the guys at performance about how to figure out the correct size for you.
The best piece of advice so far is the flat repair. Patch kits are cheap but for beginners just brink an extra tube or two in a backpack and a small pump. As CE said know how to change the tube. Although the PQ trail is so well travelled that someone will be able to help you within a few minutes of your flat.
Another nice starter trail is the park that runs along the 52. Nice easy flat trail there as well.
Once you get your legs under you we can go up to Noble Canyon and ride.
Here is a link to some trails. San Diego is an awesome place to ride. Don’t listen to any BS about mountain biking being dangerous or any of that crap. It is no more dangerous then riding a bike on cement, it is all just how much you want to challenge yourself on the trail. On PQ and the park off of 52 you can take your kids on a big wheel and they will be safe.
