Don’t expect to make it from Richmond to D.C. in 1 1/2 hours. Make it closer to 2 1/2 with traffic most days.
If you are working in McLean and live in Virginia, your commute shouldn’t be too terrible. Not great but if you live in Arlington, should be less than 30 minutes each way (possibly less depending on where you live in Arlington and where in McLean the office is). If it’s a summer internship for 2-3 months and all other factors are equal, it would be cool to be in the DC area. Don’t know a ton about Richmond, but it seems like there would be a lot more to do in DC. It would cost more, but would seem to get a better overall experience.
In DC area, you have a number of trails to run, Nationals are playing, Caps might be in the playoffs at that point (May-June) - Chinatown is a great area anyway where the Caps and Wizards play. For non-sports stuff, if you like politics, lots going on there and plenty of free museums around the Mall.