If the match against Pompey a league club is anything to go by please do not expect any hospitality like away fans are afforded at Altrincham because you will be sadly disappointed.
A couple of years ago when Josh played for Telford we drew Bristol City in the FA Cup.
My wife and I + Josh's girlfriend turned up at Bristol's supporters club for a drink and were turned away as no away fans were allowed in the premises, to be told there are a number of pubs down the road. We seemed 2nd class citizens!
Well 3 of those pubs had bouncers on the doors and did not welcome away fans. WTF were they expecting us to do? We were not allowed in!!!!!!!!!!!
Eventually, we were let into a small back street boozer in Bristol by the land lady who was a lovely person and we had a good time talking to some Bristol City fans.
Sadly league football is not like non league football where you can have a good old natter to opposing fans without wanting to punch them! SBL
I'm a Portsmouth season ticket holder, Sadly you are correct the licensing regulations at Fratton park do not allow us to admit away supporters to the club and there is no alcohol for sale to any fans in the Milton End as the very limited catering facilities are within sight of the pitch.
Portsmouth however has a lot of pubs and I'm not aware of any that actively ban away fans (excludes Southampton matches!), and whilst there are always exceptions I doubt that you would receive other than a welcome.
For what its worth as a travelling Pompey Fan we were directed to the Doncaster Rovers club as the place to get a pre-match drink but banned from Harrogate Towns club. It didn't really matter as they couldn't feed the electricity meter with enough 10ps to keep the leccy on for the tills and floodlights for the 2 hours we waited, so we went to the local pub!