If you live in LA you'll need to go over at least one highway.
Edit: ITT many Americans telling me of how walkable and great their towns are. I'm happy for you but comrades, I've been to the US once and that was on a trip I won in high school so don't expect me to know the zoning plan of Providence, Wisconsin Pop. 235'489. I don't really care how lovely your city with two buslines is. For every Seattle or Chicago there are 34 Cincinnatis, Houstons and Las Vagases and approx. 234 exurbs and suburbs.
How much of those are associated with Harvard or MIT ?
Neither Harvard nor MIT is in Boston.
Cambridge is pretty walkable, though, throughout the city with a relatively small section that is an exception due to McGrath Highway cutting through, but you can still get around.
Somerville is extremely walkable throughout the city, with no reliance on it being a college community.
Downtown Boston is very walkable, in the old parts like the North End, extending westward into DTX, the Theatre District, Chinatown, the Leather District....it's actually much harder to drive than walk in the area, but people still insist on driving everywhere. But that's probably because it's difficult to get into the city without a car.
The parts that are less walkable are places like Roslindale, West Roxbury, Mattapan. Some parts of Jamaica Plain, Roxbury and Dorchester, too.
But I'll grant you that because of BC and BU, you can walk most areas pretty easily around Comm Ave in Allston/Brighton, even as you get away from downtown. Because of Northeastern much of Huntington Ave is walkable. Looking at Dorchester, though, it seems many of those areas would be pretty neighborhood-ish and walkable even without the universities there.
For us, it's just difficult to go between neighborhoods because of our crumbling infrastructure and our limited public transit. The trains just don't go conveniently between population centers.