I'm not sure what gates UA use but the AC is close to gate 23.
My understanding if you are a member you can use it regardless of who you fly on. It's a nice club with open bar and decent snacks. The internet computer is ancient though.
Security took a bit longer than I thought it usually does and I'd allow an extra 15 minutes. Hey, if you get through early use the club and have a drink.
Good luck
DR