You can keep track on the
airnow.gov site.
Red is pretty unpleasant to be in at all, Orange can be tolerable if you're not sensitive and stay indoors and don't go outside and exercise. My girlfriend's mom left the bay area for PDX on friday because the AQI was up around 300. She's not in a particularly sensitive group, but that kind of air is just plain bad.
If the advertised rain shows up as already mentioned, it would be fine.
Definitely get masks before you go (and bring them as gifts). You probably won't be able to buy one anywhere in the bay area - there's even a lag to get them on Amazon.