So San Francisco is kind of quirky in general and weather is no exception. The biggest piece of advice that I can offer you is to bring layers! Trust me on this. It will seem as if the temp changes from block to block and you'll want to be able to peel off/put back on your clothing at will. Summer months to the rest of the country are typically chilly in San Francisco. Our "summer" months are more liky Sept./Oct. and even then, 80 is hot to us. Don't think of LA weather when planning your SF vacation. Evenings are always rather chilly, especially the closer you get to the water. I carry gloves in my purse at all times. You don't need ski gloves or anything, but just a pair of lightweight gloves is great to keep the chill off of your hands. Bring a good coat. Again, trust me of this. If you choose not to, you'll be one of the people buying a "SAN FRANCISCO" fleece pull over from one of the vendors at Fisherman's Wharf because you're freezing your tail off and shivering in the middle of July. And aside for a few occassional heat waves, you likely won't need multiple pairs of shorts. Bring a pair but no need to over load the luggage with those, sun dresses, etc... Again, you'll be shivering at the cable car stop in the middle of summer while the rest of us are in coats. Don't get me wrong, short sleeves and such are still good to have but don't pack as though you're going to be spending your days in 85 degree weather. :)
Definitely check the weather on www.weather.com leading up to your visit to see what is going on to help you better prepare. Remember: "layers are my friend!"