I have at&t if i put my regular 3G sim card in an at&t go phone will it work?
Yes, I have in the past. Haven't tried it lately. Their both AT&T so they should be compatible.
The 3G sim card might not work on your AT&T go phone since it might be under some company code lock. You should visit the customer service department of the AT&T organization to determine how you can use this sim card easily.
Not sure but I didn't think Go Phones had a spot for a sim card.