San Francisco - Best way to get from SFO to Vallejo

I prefer flying into SMF, but it's usually cheaper into SFO. How close can I get to Vallejo on BART or CalTrain? Travel time and approximate cost?

if you go to

www.511.org

and put in the address in vallejo you're going to you'll get a better idea of times

basically it's BART to El Cerrito Del Norte, then a bus # 80

cost approx $15

How close can I get to Vallejo on BART or CalTrain?

BART to El Cerrito Del Norte, and then Vallejo express bus 80 right into Vallejo (you could do it via Walnut Creek BART but that bus would have to come through Benicia before heading over to Vallejo and take longer). I would caution you that the bus does stop in some areas that I would consider unsafe so hopefully you would be having someone meet you at the bus stop when you arrive.
http://www.vallejotransit.com/routes.html

BART could take you from either SFO (inside the airport) or OAK (via an 8 minute connector) to either the El Cerrito Del Norte station on the Richmond Line or the Pleasant Hill or Walnut Creek Stations on the Pittsburgh/Bay Point Line, from which you would need to catch a bus to Vallejo.

You wouldn't want to get off the train in Pleasant Hill as that bus, after it arrives from Benicia, continues over to Walnut Creek BART before turning back around. I always get the bus in Walnut Creek to avoid that extra stop.

If you really want to take the long way around, you could do BART to Richmond, change to Amtrak to Martinez, and then Amtrak bus to Vallejo. :D