There a few places here you can rent bikes from. I know Harley's can be rented for sure - maybe BMWs. May be a couple other places but there are not a lot of options.
A little unsolicited advise: Don't know where you are coming from, but Vegas in May can already be hot. Too hot for most people who are not acclimated. Riding anywhere in the heat and super low humidity will cause you to dehydrate super quick. Cover up and drink way more water than you think you need.
Valley of Fire should be everybody's number one place to ride through and explore. Truly amazing. Hoover Dam. Red Rock. Death Valley, but take note of my pervious advice. There are no good riding roads around here. Almost everything is straight for miles and miles and miles. Gotta get up into the mountains for twisties. Head to Pahrump (little fun). Mt Charleston is Ok too for some twists and turns. If it rains, it is like riding on snow & ice.
The Las Vegas Motor Speedway. Shelby museum. Arlen Ness.
Places that sound good, but aren't; Neon graveyard. Freemont St Experience. Atomic Testing museum. Mob museum.
If you need any more info, feel free to PM me.