West End or south Dupont. Depending on where you are, you can have a less than 10 minute walk both to the blue line (convenient once the Potomac Yard station opens) and the red line. You can use Farragut West or Foggy Bottom for the blue line or Farragut North or Dupont for the red line. And easy transfers between them from Metro Center.

That said, somewhere near Metro Center could also be a good option. I think Cleveland Park or anywhere along the red line could be fine if you're driving but might be a lot of Metroing with the schedules lately.