There's so much to see and do in the SF Bay Area...where to start?
Here's a couple websites with calendars of events for the coming weeks that will give you a flavor of the variety of things going on.
http://www.sanfrancisco.travel/
http://events.7x7.com/
http://www.sfstation.com/calendar/
Have you ever been out to SF before? Interested in hitting the popular tourist sights? Late March through May is sort of "festival season" with street fairs/festivals going on, Cherry Blossom Parade in Japantown in April, Bay2Breakers in May, etc.
March can be a little hit-or-miss, especially this year. We're supposed to be having an El Nino winter, which means more rain than normal, but it seems that the heaviest part has already passed -- people are guessing whether March will be rainy or not. Also, lots of people in SF got up to Tahoe on the weekends this time of year. Not that the city will be empty by any means, but you might hear a lot about it. OTOH, you might find some restaurants and bars being less crowded on the weekends.
As for places to stay, all the major hotel chains/brands are around Union Square: Marriott, Hilton, Hyatt, Startwood, Kimpton, etc. If you have a preferred brand, look for their property around the Union Square area.
Feel free to DM me if you have specific questions.
Enjoy!
SFGate, check out "Top 100" and "Cheap Eats". Also Heatmap, Eater 38 and similar. For foodie shopping, The Ferry Building, Pier 1, is the place to go. Also check out "neighborhoods" section in SFGate.