Try the gardens at Dumbarton House or the National Arboretum.

If you buy a hummingbird feeder from a garden store some of my neighbors near rock creek have gotten hummingbirds on their back porches when they put one up for the season.

https://www.hummingbirdcentral.com/hummingbird-migration-spring-2023-map.htm

I saw about four HBs within fifteen minutes in Rock Creek Park (near Peirce Mill, along a hill next parking lot 1) last year. Hope you spot some!

I saw them in New York as a kid. #blessed

I'm out in the burbs, we have regular visitors starting in mid to.late May. Here's a good reference to watch https://www.hummingbirdcentral.com/hummingbird-migration-spring-2023-map.htm

I lived in old town Alexandria the past few years and regularly saw hummingbirds in my yard and my neighbors’ yards. They’re attracted to any area with lots of flowers that produce nectar. My go-to hummingbird plant is zinnias, especially the giant ones (you can grow them in containers if you have limited space). They grow amazingly well in our hot summers and attracted hummingbirds as well as goldfinch. I would see hummingbirds several times a day for months, although I typically didn’t start seeing them with regularity until at least late May/early June. If you’re trying to see them in Alexandria I’d suggest walking through the alleys behind the houses rather than the sidewalk in the front as you’ll be more likely to spot them in the flowering trees and there’s fewer people/traffic to scare them off. They can be shy so if you can find a spot that is relatively calm you’ll have a better chance of seeing them. They have to feed very frequently so if you figure out where they feed you shouldn’t have to wait long to spot them. I used to see mine about every 2 hours starting around 6/7am. Good luck!