I can make some generalizations, but as with many things, individual situations may vary widely.
Mosquitoes: The City of Fargo and neighboring jurisdictions have become much more agressive about fighting mosquitoes since West Nile virus has become known as a threat. There is usually a public awareness campaign every year about getting rid of standing water, keeping grass mowed, and the other things that homeowners can do to keep the population down. When the counts that are officially taken get too high, they do spray in the evenings. A truck with a mister will slowly drive up and down all the blocks in a region of the city. There have been a couple of times when the whole metro area has cooperated with aerial spraying, which has been really effective.
Drivers--it's not so much an issue of rude drivers or road rage, as it is of thoughtless or clueless drivers. I've talked w/ people who have lived on the coasts, and overall they would say that drivers in busier urban areas are much, much better. Perhaps it's due to the fact that a driver, in SoCal for instance, knows that there will _always_ be other cars present. Here, you defintely have people merging in without looking at all.
Dogs--in my neighborhood they tend to be small house dogs. I haven't ever encountered dogs just roaming--cats, yes, but not dogs. There are leash laws in Fargo. There's more official info at the City's web page on pets and strays:
Pets and Stray Animals - City of Fargo