Not an official link so look up "USNA Summer Training: 2/C Gray Hull Cruise and Other Adventures" on a site called Navy Online. It's a good overview. Other posts are correct - can be any location - one sub cruise was from Pearl Harbor, others east ports/ locations etc. Ships - heard of SWO cruises around the world - Asia, Europe, San Diego, Virginia - both US Coasts, etc.
Sometimes subs pull into port to begin a 2/c summer cruise, but subs are appropriately fanatical about OPSEC and protection. My DS was brought out to an unspecified location in the Pacific a couple of hours offshore, via I kid you not a nondescript tug boat, and out of nowhere seemingly a LA class sub arose from the depths next to the tug, a platform was extended for him to board. Then very quickly they auuuuga- auuuuga (Claxon sound) battened all hatches, re-submerged and off they went for that summer cruise. I thought that was a lot of fun.
Good luck.