We’ve ubered to Riviera, and more often, taken the skyliner. We’ve never stayed there.
We’ve had success at Topolino’s bar.
There’s bar seating, plus a few tables in the lounge area. It’s not a huge space, but pleasant enough. We’ve visited about 5 times without ADR’s, and have never had trouble getting a spot in the bar area (usually a party of 4). YMMV, however.