I am going to US , LA and San Francisco , in late July, I would like to know if the GPS location services is still available if I have the offline SF google map downloaded to my cell phone and have my GPS turned on ???
Yes, you can still use GPS to locate yourself. The google map in offline mode does not have that many details. Noted that the time to get a GPS lock might be a bit longer (might take minutes) because you do not have data connection (AGPS cannot be used).
You can check out the Osmand offline map app also, not as good as the google map but can be useful when you are offline.