This was me 2 years ago. Masters workouts were more (way more, usually) than I could do but it was a pleasant enough experience. Not Arlington, though.

Here's a place to start, both for a workout plan and just getting familiar with some of the terminology:
http://ruthkazez.com/swimming/ZeroTo1mile.html

With a solid fitness base from running, I can work up to the mile pretty quickly with just one or two swims per week. (As in, number of weeks to do it ... it's still a slow mile.) I start with her week 2 or 3 workout and just increase from there.

I only swam with a masters team for one season but I wouldn't hesitate to do it again if I wanted more swimming or serious improvement. I would probably start with the routine above and try to get some of that early awkward swimming out of the way before going to a group session, but that's mostly because you'll get a lot more out of the session that way.

I swam for a few years as a kid on a swim team and now that my kids have started swimming lessons I was curious about getting back in the pool. However, I am completely intimidated. Is anyone familar with the masters swim program in Arlington? If I show up for a practice will I be too slow and get in the way? I took a look at their sample workouts on their website and it is completely foreign -- I have no idea what the terminology means. I need to get a proper swimsuit and googles too. Any suggestions?

BTW, I run regularly and race (up to 1/2 marathon distance), but I need to add more cross training. I know swimming will completely kick my butt which is also why I'm intimidated.

Thanks in advance!