The brunch in the Renaissance is good - but as Duffy noted, you'll pay hotel prices.
Your best bet for a nice brunch that won't cost an arm and a leg in cab fare is probably the Grand Concourse in Station Square on the other side of the Monongohela. It's easy to get to by trolley - one or two stops either Wood St. or Gateway stations. The T fee is two bucks. Plus the building is a converted railway station and quite ornate. It's a local favorite.
If people are going off on their own and craving pancakes and eggs, then yeah, the Strip is the way to go. But if people want to dine as a group, that probably won't work very well.
Another excellent option is Sunnyledge, northeast of the Pitt Campus on Fifth. It's a rambling old B&B with a good brunch spread. But that's a cab ride.