Yes, any good Realtor can (and should) be able to help you with both the selling and the buying. It's a complicated balancing act of timing and organization so you want someone who can map out the best strategy for you.
Earlier this year, I helped clients sell their home in Portola so they could buy a bigger home in Bernal Heights. Actually, they found me on Trulia! :)
Depending on your individual situation, it could be a smart time to "trade-up" b/c even if your current home has lost value, you may save even more on the next property.
With proper presentation and pricing, homes in the Excelsior are selling.
See the link below to the Q & A from the home sellers in Portola. There is a lot of info on the balancing act of buying and selling these days.
Please check out my online client reviews at http://www.yelp.com/biz/danielle-lazier---zephyr-real-estate
and give me a call so we can discuss what you're trying to achieve and see if we'd be the right fit to work together. No pressure.
Danielle Lazier, San Francisco Realtor
Zephyr Real Estate
danielle (at) zephyrsf.com