The entrance to Bootleg Canyon is just blocks away from All Mountain Cyclery. They do rentals as well, so you can rent and ride to Bootleg straight out the front door!

If you're staying in Vegas without a car, there is really good public transportation to Boulder City. You can be there by bus in a little over a half an hour. It's totally feasible to bus from Vegas, rent a bike here, ride Bootleg, then bus your un-showered ass back to Vegas without walking more than a couple of blocks. If you catch the bus in the right spot, you can do it without any transfers too!

This is a really great option for those in Vegas for a conference that want to get a ride in. Sadly, Red Rock Canyon was inaccessible from Las Vegas by public transport of any kind last time I asked.