If by "mesquitos", you mean the flying insect also known as mosquitos; I HATE THE LITTLE BLOOD SUCKERS!
As far as bat boxes go, I have never had luck getting bats to use them and know of no one else who has either. However, they will nest in attics and other areas you don't want them to be in. From my research in trying to get bats to use the bat box, you want to mount the bat box onto the southern side of something, whether is be a home, barn, outhouse, etc... That way in the winter, the southern sun warms their home.
Depending on what part of the country you're in, you may also want to look into mounting a purple martin home. If you have a fairly decent sized pond and open grassy area next to it. A properly mounted purple martin house should be prime real estate and a new family should gladly take to it. Purple martins like wide open space, no large trees or other structures near their house. Check into that option as well... They certainly will thin out the flying insect population to include mosquitoes.
