No Dogs
Dogs are not allowed in Somerville city parks (Code of Ordinances, City of Somerville Sec. 12-51. Dogs in parks and playgrounds).
The Dog Lover's Companion to Boston: The Inside Scoop on Where to Take Your Dog, 3rd edition, by Joanna Downey (Avalon Travel Publishing, 2002) lists dog-friendly things to do and places to go in Boston and surrounding areas. Unfortunately, the entry for Somerville is pretty short:
Okay, we looked. And looked. And looked. Where do you poor folks in Somerville take your dogs? Every park we found has a No Dogs sign big as day, and all the secret spots where locals told us we could go were given the big thumbs-down when we spoke to city officials (97)The entry does go on, however, to mention dog-friendly cafes and bakeries where canines can eat well in Somerville.
Nearby, in Cambridge, according to that city's website, there are dog runs at "Fort Washington, located on Waverly Street between Erie Street and Putnam Avenue, and at Dog Park, at Mount Auburn and Hawthorne Streets. There are also leash-free zones at Danehy Park and at Fresh Pond Reservation. . . At all other parks, the City ordinance on leash control applies. And of course, dog walkers are required to pick up dog waste at all sites."