I agree with @gottagrey - if you’re really around the middle (e.g. around WH, Capitol Hill or surrounding areas) I’d strongly urge you to consider options in SE MD, perhaps around Prince George’s county, as that would be much more feasible than driving to Leesburg/M-Burg/Gainesville areas. We used to live very close to Capitol Hill and getting to barns in that area in morning/evening could take anywhere between 25 and 45min depending on traffic. Middleburg on the other hand was a bit over an hour on a weekend. My doctor was located in Chevy Chase (direction of Bethesda) and I gotta say the traffic is awful there, I’d never get there in shorter than 40min no matter what time of the day. It’s also city driving (to Bethesda) vs. not too congested highway (towards SE MD), which makes a huge difference in commute quality.
I’m sadly not in the knows of pure lesson barns (as we were boarding), but can recommend this show barn http://www.bayviewfarm.org/, which I think has a couple of horses that they teach on. The trainer, Alison, is really nice and from what I can tell very competent (her daughter did GP jumpers). It’s a good place if you’re interested in getting back into the show ring. I’ve seen Liberty Ridge Stables in that area offering lessons and half leases too, but I believe they don’t have an indoor so that might be a no-no for you. Looking at their sales videos though, again, I’d definitely check it out if I was getting back into the swing of things.
All of this might change if you live in Georgetown or even more West.