@pengsphils - Great map! Never seen that one before.
The 15 minutes I quoted in Google maps includes the time to walk to the public bus and take it to Davis Square as well as the subway time between Davis and Harvard Squares. For students, Tufts runs a continuous shuttle (with a cell phone app to show where it is) between the campus and Davis Square - so that is more efficient than walking to the public bus stop.
Note that the city of Somerville is small (4 square miles), but it is ranked 15th in the US in population density (more dense than San Francisco, Cambridge or Boston). So if “urban” means lots of people, then Somerville fits the bill as well.
https://en.wikipedia.org/wiki/List_of_United_States_cities_by_population_density
Tufts also runs a shuttle to the New England Conservatory and Museum of Fine Arts (they have joint degree programs) so there is no excuse for your Tufts friends not coming to visit you- even if they don’t want to take the subway!
My daughter worked 20hrs per week downtown at an internship during her senior year at Tufts, but it all depends on the individual. In general, students tend to venture into Boston more often with each passing year.
In 2020 the Green Line extension (from Lechmere) will place a new subway station on the Medford Side of the Tufts campus providing easy access to both the Green and Red lines.