Can this frame be salvaged?
 

Last year I was a little negligent and let my jamis dakar sit out in the san francisco fog and rain for a bit too long. It's got a lot of rust in the bottom bracket (also missing a bushing in there), chain is obviously rusted,and what worries me most is a large dent on the downtube that i assume is from someone attempting to steal my bike (thank you, kryptonite lock). There's a hairline crack in it and i don't know if it's even safe to ride.

Pics are here: http://img200.imageshack.us/gal.php?g=bike001d.jpg

I'm pretty much a noob with bike repair so some guidance here would be awesome and really appreciated.

+1 Goner, as far as I can tell from the pics.

I don't see the crack. If the other components are like the chain you have screwed the pooch and need a new bike.
I left an old Raliegh steel road bike out 24-7 for 7 years in the refinery in Texas City in the salt and chemical air, but I took care of it and rode it every day.

Where's the crack? Show a close-up picture. the hairline crack may be just in the paint from the theft attempt. Pick off the paint in that area and see if the metal is cracked as well. One of the benefits of 7005 aluminium is it can be welded without needing post-weld heat-treatment like 6061.

As for the bike, it's definitely salvageable, depending upon how much work you do yourself. A complete overhaul is all it needs, about $100-200 in parts and $200-500 in labour at a shoppe. Comes down to whether you can buy another bike in comparable post-repaired condition for a similar outlay.

i couldn't ride a bike if i thought there was a crack in it, get it checked out at your LBS if you're worried.

p.s. at the drive-in rule :thumb:

I'd check the frame alignment before deciding on whether to weld or not. If it's straight, go for the weld. If it's not, toss it.