I'm OK at the moment, but if I wasn't I think my desire to leave wouldn't really be about going outside, but wanting stimulation, people, something to do or **** with. I think that a trail is a good idea to start with, but healthy exercise can intensify manic states as often as diminish them. Trying to find out which would happen with your friend would be good so you can prepare.

Although this is in no way recommended by the CDC, some kind of personal interaction might be good. This all depends on your risk tolerance but if you know people who have quarantined well enough to not be a high risk, and if they are OK with you and your friend, then social interaction would likely help a lot. If it were me hypomanic I would leave my house. No question. The questions you have are if and how you control it.