Heading out there for a week, not sure what to expect other than soaring temperatures. Not much has been said on bikeforums about riding in the area.
I'm more of a roadie this time of year but I could take a mt bike instead, if that's preferable. From the map it looks like big climbs on the east and west sides of Bullhead City, but I'd bet the highways are the typical desert experience-- too fast and no one pays attention. I cant find much of anything on trails out there.
Was just in Boulder city... north of there. Perhaps the nicest rides in the area are the isolated two lane blacktops just south and east of the lake in the Lake Meade rec area. You may want to take a drive out that way and then go off on your bike.
I found that even though the traffic was fast, it was few and far between, and you could hear them coming from a good distance. I rode very early in the morning.
I live in Bullhead City, can give you all the details on riding, unless you are coming after October 1, it will be hot. If you like to get up early, its not too bad. Lots of climbing on road or off road, and there are just all sorts of dirt trails to go exploring. Road riding isn't too bad, especially this time of year mid week, snow birds are gone, and the boat traffic is more of a weekend thing. And if you ride early, well just less traffic. If you want some specifics, send a PM and I'll fill you in.