One of the best sources of info on bats is Bat Conservation International: http://www.batcon.org/
If you have a bat house full of bats and you need to move it, you should do so during the winter. Your profile says you are in northern California which means your bats likely spend the winter in a cave or mine somewhere, or perhaps an unheated attic.
Bats usually prefer houses that get a lot of sun, thus a north-facing location is kind of unusual. But they do move roost locations frequently based on temperature needs, parasites, etc.
I am pretty sure that bats do not eat wasps. Little & Big Brown bats eat mostly night-flying insects such as moths, beetles, mosquitoes, etc. I have never heard of one eating a wasp. Wasps do build nests in bat houses, but generally speaking the bats and wasps leave each other alone, even when sharing a bat house.
In the wild, most bats in North America roost under bark that is exfoliating from dead trees (during the spring and summer), or in cavities in trees or cliffs. Thus any location that resembles exfoliating bark will seem like a good roosting spot to a bat. As Gwen noted, closed patio umbrellas are a good example. Other common places are behind loose siding (especially cedar shakes), in wood piles, under barbecue covers, etc. When they cannot find tree cavities they will use attics, wall cavities, and yes, belfries.
It is rare for bats to get rabies (something like 0.5% of bats will ever get rabies). If they do contract rabies they do not live long, so the chances of you encountering a sick bat are slim. But if you ever see a bat on the ground, it is probably sick or injured, and whatever you do, do not pick it up with bare hands. Like any wild animal they will bite you if you try to pick them up. BCI has a good page on dealing with found bats: http://www.batcon.org/index.php/education/40-bats-and-the-public/67-living-in-harmony.html
If you are interested in bat houses, there is a great bat house discussion forum here: http://bathouseforum.org/
How does one move a bat house full of bats? I thought I had found the perfect location under the eave at the peak of a two story roof on the north side of the house. Cooler in the summer and protected in the winter, but evidently they poop just as they fly back in and it gets flipped onto the house and nearby window. I thought it would just fall straight down and I could catch it there and use it in the garden! Anyone with any batty ideas?