More often than not we ended up cabbing over, I think we found that cabbing to/from the Flamingo was the cheapest and most direct route back and forth. We thought about going over to the Gold Coast shuttle but never did so I don't know how frequently they run. The shuttle only holds about 30 or so people so you can gauge by the number waiting ahead of you how long you might have to wait. At worst you would end up waiting for two trips, since they run every 15 min it would be half an hour to get over. I just got back from staying at the Rio and found that there did seem to be some peak times where the shuttle lines for Harrah's were long.