The climate in San Francisco is quite mild, if a bit cool, but not so cold that you cannot enjoy a long walk year round. The temperatures average in the 50s and 60s and, while you may get a few temperatures higher and lower, you won’t see a lot of extremes.
The terrain in Sherwood Forest is not for the faint of heart and, if you or your dog are out of shape, you may find that you will have to make some adjustments in order to make walking safe. Keep in mind that this neighborhood is on the slope of Mt. David, so don’t expect much in the way of flat terrain. If you are just starting out, you may just need to adjust how long you walk and plan things out beforehand.
Your other option is to find a park with flatter trails, at least until you are up for the terrain in Sherwood. If you and your pup are more fit, then you might feel right at home. Steep terrain will be great for getting your daily work out. Keep in mind that you will be walking mainly on concrete. There are sidewalks, but not a lot of landscaping that is not on private properly.
Sherwood Forest residents are fortunate enough to be right at the base of Mt. David which is the city’s highest peak as well as a beautiful park filled with walking trails. Several of the trails and one of the park entrances open right on the edge of the neighborhood, making for easy access for walkers.
Further to the east of Mt. David is Glen Canyon Park, notable because of the presence of a dog park. It is a bit of a drive, but close enough to make it a good alternative if you and Fido are looking for a change of pace. Glen Canyon is a deep canyon, so it also makes a nice alternative for hot days when hiking to the top of a mountain may be a bit more than either of you are up for. Keep in mind that, since this is a deep canyon, much of the hiking here is also pretty intense.