I've written to my local library organization suggesting cafe areas in some of the bigger libraries. Never heard back, but I really hope they think about it. It could raise some money and improve patronage. The local library is much more convenient for me than the coffee shop, but I need to be eating/drinking when I'm working on something.

If you're near a University, check out their library. Most of the time they'll have a cafe, guest wifi, and a reasonable amount of white noise for a library.

I was surprised when I found that the library close to my place in London (at Swiss Cottage) has a cafe inside and seems to have a relax policy on eating snacks inside the library.

For the silence/ambient noise problem: http://coffitivity.com/

They also appear to let you bring your own food and drinks. I've seen moms break out a box of Capri Suns to give to their herd of children and people unwrap a footlong from Subway in the Barnes and Noble Cafe.

I've worked from a library a few times recently. Security is important, but there are libraries that don't have this problem (might depend on the country, though).

Other points I personally regard as features that help me focus. If wanted to get some food, I'd go to a café. To meet someone in person or make calls, an open space (if there isn't any, a café) is a decent option. But if I want to concentrate on something for a couple of hours, I personally go to a library.

This hasn't been a problem in my experience in Chicago (and to a much greater extent Oak Park). In both, there were lots of homeless people around the library --- but they weren't at the same table as you, and they didn't disrupt anything.