Spanish Steps is a cool spot to hang out over drinks on a beautiful/sunny and hot day. It's just outside the entrance to Caesars and right next to Serendipity 3. They have a good selection of Mojitos and can make them with different flavours. My mate had a few of those and he said they were pretty good.
I like it. It's quite pricey yes but you should at least try one of their mojitos I reckon..