What time of year do folks join teams? And any come/go?

Kids' schedule will not permit me to join a team, but I am thinking about checking out the local team during their noon practice, and maybe doing it for a month here or there (they may not let me ). The question I have is, is there a "beginning" of the season where they have new members, or when they have breaks, or otherwise is there a more ideal time to join? There is not a whole lot of info on the local team's page. I am also wondering how open teams are to folks dropping in for a month at a time. So maybe I'll swim for a month out of every 3 or so. I'd like some coaching, and some help in pushing my limits (hard to do on one's own). But I can't do it throughout the year, as the morning and evening practices offered conflict with my kids' practice. I know right now, USA Swimming is in between the end of short course, and the beginning of long course. Don't know if USMS has a similar break.