See if you can rent a Mustang GT, preferrably green, and blast through the streets of San Francisco trying to get as much air as possible./forums/images/icons/smile.gif
Seriously, there is an automotive museum in Blackhawk (Danville, east bay) that has some really exotic cars. Check 30 or 40 posts down the forum as some pictures are posted.
With all that S.F. has to offer, you can easily be entertained with things non-Mustang related. If you want to go to Alcatraz, call and make reservations for a tour. Hit China Town, Fisherman's Wharf or North Beach (Italian) for some good food. Some natives can fill you in on less touristy things to do.
As far as Sacramento goes, Old Town is pretty cool. Sacramento natives will certainly chime in with specific things to do.
In Sacramento you can get on a raft and float down the River if you like. You can also do my favorite thing and go drool over the counter at Sacramento Mustang parts. Now if you are really bored you should go thru the junkyards down there. They have some of the biggest. I doubt that you will find Mustang parts though, but if you ilke you can locate some Saturn parts for me!
For car related: Check out the Towe Ford Museum downtown. It is pretty cool. Along with the the conistant display of cars they usually have "guest cars". I dont know if they have a website but you can call 916-442-6802 for more information. Since you will be downtown, you should take a walk through "Old Sacramento". This is a historic part of town right on the Sacremento river as it would have been during the gold rush. From there you can walk to "new sacramento" and the K Street mall. An open air mall - nothing special but kind of cool. There is a Hard Rock Cafe there.
Sacramento is also the State Capitol. The Capitol and its grounds are very cool to check out. Around the capitol is a huge park with many memorials and gardens.
Sacramento is a huge urban sprawl, so without knowing where you will be at it is kind of hard to point you in the right direction.
If you are in town for a couple of days, out toward the Folsom area there is a car show every Wednesday nite at the local Red Robin. This is hosted by a car club "the cappaccino cruisers". I havent been this year at all. maybe they have a website to confirm time and day.
I'll second BlueMach's advice of checking out the Towe Auto Museum. It's no longer just Fords (it used to be the Towe Ford Museum), but is still mostly Fords including a Boss 302, and a Shelby Mustang.
Next Saturday night we'll be going to the Grass Valley Mustang Club's show. You being in El Dorado Hills, ought to come along and check it out. A little longer drive for you, than it is for me being in Roseville, but PM me if you're interested.
There are some great driving roads in the SF Bay Area if you have the time for a cruise. In the north, you've got the roads to Stinson Beach and Point Reyes, in the east, you've got the roads through the Berkeley and Oakland Hills (Skyline, Grizzly Peak, Fish Ranch Road and many others); on the peninsula, you've got Highway 1 south to Santa Cruz as well as Skyline (highway 35). Get tour AAA maps out and plot a course!!
In San Francisco the only thing Mustang related would be to come look at my Mustang /forums/images/icons/smile.gif Nothing really car related here but a lot of good tourist spots. Lombard street (not really the crookedest street in S.F.) You can take our scenic drive. Fisherman's warf. (You can park at my house and walk, I won't charge you anything /forums/images/icons/smile.gif ) Cable Cars, Coit Tower, Golden Gate Bridge, Ocean Beach, Presidio, China Town, Northbeach, Castro Street (maybe not for some folks), Downtown or Union Street for shopping. There is alot more but my fingers are tired.
Go to Ft Point (under the Golden Gate Bridge), Palace of the Legion of Honor by the Presidio (great classic museum), The Exploratorium (fantastic hands-on science hall) lunch at Beach Chalet on the Great Highway (south the Cliff House near the giant windmills), or Pizza at Villa Romana (on Judah or Irving down from 6th Ave).
See the old-fashioned coin-operated games at the Cliff House called Musue Mecahnique (sp) (lower level, at back, go down exterior stairs to access). Go up to Twin Peaks (only if its clear, fat chance in summer)
Baseball fan? You can watch the Giants game for free (there supposed to be a time limit however) thru a viewing area in the right-field fence, check schedule first.