Brockton
I grew up in Brockton. Hopefully your moving to the decent part ;-). That being said, there use to be a sick gym that had a dungeon feel to it. Lots of big mofos in there too. Was called centre st gym I believe. I would look into it and see if its still there. It was right near the police station.
There's a gym in Braintree ma which is 2 towns over called bayshore and its a great gym. Lots of competitors and big dudes up in there. Best gym on the south shore IMO. Depending on where your gonna be in Brockton it could be a 10 minute drive or a 25-30 minute drive. Check it out and if its not too long a drive, I would join. There's guys that drive 30-40 minutes to go there. Hope this helps.