Good luck. As has been mentioned, try it and see if you like it. If you're looking for a social environment that won't improve your game a whole lot, go for it. If you have another choice, such as BCA, I would strongly suggest you try it instead.
Afraid I have to disagree withe "won't improve your game a whole lot" comment. In any league, and in any game, a player will improve based on their will and drive to improve. If the player wants to improve in APA, or any other league, they need to have the drive to work, practice, and improve.
They can learn from the better players on their team, learn from players on other teams, or go outside the teams and meet the better players who are regulars at the halls they play in. It just requires initiative, and it doesn't matter that they are choosing APA, BCA, or some bar leauge.
In my aread, I learn alot from my team captains, who are competent players, but not money/bar players at all, and that's fine. These guys give me plenty of strategy advice, and give me plenty of challenge when practicing. I was a decent player before entering APA, now I'm definitely a more solid player after joining the APA.
Putting the above aside, I've also come to know all the "serious" players in my local halls, and when I want to work my more serious game, none of them have any problem practicing with me, helping me, and giving me advice. And these guys will do this with anybody in the APA, anybody who seriously wants to improve.
Yes, different leauges can attract certain types of players, and I expect some leagues to have somewhat of a higher proportion of strong players than leagues like APA. However, if the original person likes what the APA has to offer, then they will lose nothing by playing in the APA... And unless there is something different with the player makeup of their region compared to the other regions, they will have plenty of people to tap to improve their game as far as they want to take it.
Of course, many people on AZ are money players who play traditional TE 9-ball and one-pocket. Many of those players complain that APA doesn't have real 9-ball. It's true that APA has it's own 9-ball game that is just a points game for the win based on the total number of pocketed balls for each player. But nothing stops a player from applying TE 9-ball strategies and technique in their APA games; the points ultimately rule the match, but I play like I'm playing plain ol' 9-ball... Nothing is stopping me from doing so.
I guess I could just have said that any person will get everything out of APA that they put into it. It will take time to settle in, meet people, and to find the right people to get advice from, but that would be true whether they did it via APA or any other leauge.
Cheers.