Here is my experience in brief:
I had 2 appointments only for myself and my spouse at 11.30 and 11.45. Took BART from easy bay and got down at Montgomery St. Follow signs from BART to goto SanSome / Sutter. Once you are out from BART walk through SanSome Street. After 6,7 blocks (8 min) you will hit Washington intersection.
In some other posts I read that I had to goto SanSome street entrance. BUt its wrong. They told me to enter through Washington street. While waiting on the secutiry line, I noticed that there are 3,4 street parking (meter) lots available just in front of the INS office. Washington St is one-way towards SanSome.
Secutiry people are tough (their job). I noticed that they even didn't allow a sick women just like that. We need to remove everything except cloths
Belts, wallet, keys, phone ( i didn't take my camera phone, rather took the usual one), spouse bangles everything needs to be removed.
After this, there are 3 counters for processing your infopass application and giving away tokens. They ask your approval notices and info pass printout. They they will give a token number printed and stapled with your infopass and approval notice back. Then comes the waiting area where you wait and watch for your number to come.
Restrooms and cafe are there inside for timepass. Forgot to tell you strollers are allowed but need security check. nobody cares if you take food inside.
I had all my documents ready in order. I had 2 APs and 2 EADs. I pinned them in order with 2 phots. FIrst I gave one passport with approval notice. Then she asked me "give all you have like AP and EAD". Seems she even won't know what are all I should give or may be she don't care. She verified everything and asked me give the index finger printing. Then she asked my signature. Thats it. Another application and samething.
Over all, it was a good experience.
DO NOT GO with the plan of eating at nearby Tandoori Indian Mahal hotel.