I have always heard you can, but I know I wouldnt care for someone diggin around right in front of my house. But my house also sits just 30ft from the road, and the easement between the walk and the road is cared for by me so its kind of like my property! I could see how you could tick people off detecting there, if in front of there homes.
This has been a controversial topic here on T-net before. The boulevard is city property but be prepared to be yelled at by people who think they own it just because they care for it. I couldn't care less if someone searches mine, but there are a lot of metal detectorists even on this forum that are opposed to someone searching their pieces of city property. Boulevards are great places to search, but I won't anymore unless there is construction going on. I got tired of people yelling at me (even when I was probing) but my friend is gearing up for searching them as he spends his time arguing with the people who flip out (80% women) and just tells them to call the cops already. I've had the cops called on me about 5 times from boulevards and it was waste of their time as I was doing nothing illegal and was not damaging the grass. I tell people that if they want to keep the cops from catching real criminals, then go ahead call them. It is usually because they think they own that property but they don't.
Detectorists here will worry about promoting the hobby and will not recommend that you search these grassy strips but I will tell you that if you can tolerate the staring out the window, doors slamming, and the yelling, then go for it! Lots of goodies to be found!
Dave.