For me, the trails right behind my house for a quick 45 minute lung buster. If I have the time to pack up, its
-Daley Ranch, Escondido
-Lake Hodges, Escondido
-Black Mountain, Carmel Valley area
Spend some time here, you'll get lots of ride ideas.
http://www.mountainbikebill.com/index.htm
On the left, click on SD County, he even has a North County section.
FWIW, I bought a full suspension from Performance, spent around $1K. It was nice to get started, but I got rid of that and got a hardtail. For me, I like doing longer, endurance cross country stuff. The hardtail climbs sooo much better, is lighter, and can still handle the roughest trail I want to go on. It's all what kind of riding you want to do.
Black Mountain Bikes is having a demo day the first weekend of March.
http://blackmountainbicycles.com/eve...-map-pg404.htm
If you are there on Sunday, across the street I'll be huffing and puffing my way through the XC race.
http://www.racersandchasers.com/Blac...tain_2-19.html