Dragonflies eat a lot of mosquitoes too and are a bit easier to have in your yard.

If you can find bat boxes for sale you may have to make one yourself (or have someone build you one). The dimensions are online.

I think all of our bat species are insect eaters so your garden plants should be safe.

I've always heard that if you place your bat box in the proper place (they're picky about roosting sites) and still don't get any bats the sure fire trick is to find an old house or barn that already has bats and gather up some fresh bat poop and sprinkle it directly under your bat box. They can smell the poop and will then think that other bats are using your box and swoop in to join the group.

Ewwww..gathering up fresh bat poop..Yuck

I've had a bat house up on the side of my yard barn (about 10' up) for many years and never any evidence of use by bat,bird or bug. My feeling is if they are in the area attracted to insect populations they have roosts that might be miles away.
What you get roosting in your yard might not stay in your yard to feed.
No harm is building a bat box, sun positioning and height off the ground is important as John said. I wouldn't expect much use because, unlike dragonflies, bats tend to be communal and use a lot of flight area and distance apart when feeding at night.

Now, if someone would find me a critter to eat daytime mosquitoes please. A half dozen dragonflies aren't making a dent.

I had to crumple up foil and cram in the spaces between the exterior wall and my decorative shutters next to my windows. Bats were roosting in there! They may be great insect eaters, but they give me the creeps. They are finally gone now (someone told me they wouldn't like the look of the foil) and I hope they headed your direction!

I held off taking action on making a bat box because I was pretty doubtful about there being any bats in High Point. But tonight I was out walking my dogs at 9pm and looked up at what I initially thought were birds but were in fact small bats...quite a few of them.

I am definitely now going to do my part and make a bat box and attach it to my guest house for the bats to live in.

I stopped spraying my yard with bug killer chemicals and although now there are lots of lovely fire flies there are also lots of mosquitos. Dragon flies certainly don't get the job done.