this is what I use to run down to the grocery, bar hopping, throwing on the trolley and riding around downtown, and just general cruising.
It's a Mirra Icon 20forty 24" BMX cruiser. Single speed (36x17) with street/dirt treads. It can be a bit of a challenge on the ascent, and I get a lot of hill training; I have a good 400' climb just to get back to my place from the trolley station. I just get out of the saddle and crawl up the hill, no rush. Most of my so-called commuting is under 10 miles (I can't commute to work due to MCAS Miramar) and I managed a 12 mile cruise without getting too fatigued.
The 29er will be used predominantly on trails; leisurely bombs around Sweetwater Reservoir and the like, but I'm sure it will see some cruising action down along the wharf. I just hope I can wrangle that horse onto the trolley!
In the interest of full disclosure, I'm a former BMXer who has been riding XC/trail for about 25 years. I tried riding a road bike for about a month, but just couldn't get comfortable on it. The speeds were nice, but I like the luxury of being able to hop up on the curb, or cut through vacant lots, open fields, etc. Happy riding!