People have mentioned that there aren't great bike connections to DC or to most of the surrounding area in Prince George's County. I've ridden around National Harbor a few times in the past, but not recently. I haven't heard a lot of great things about the bike network in that area. There will be 3,600 employees at the new casino, which is scheduled to open by the end of 2016.
I'm not sure how many people will be biking to the casino.