My DD2 and DD3 were really predictable sleepers at an early age until about 5 months old, when they started to wake up anywhere from 1 to 3 hours after they were put down. I realized this with my third baby that we had this window of opportunity to go out (after bedtime) when she was under 5 months of age. We went out every few weekends for a few months and just like her sister before her, at 5 months old she's been waking up unpredictibly after bedtime. So now I stay home, or if I go out it's an hour max, with cell phone beside me.
So, IMO, if you're up to it and want to go out, take advantage of the time!
FWIW, my DD1 was not predictable at all. She was colicky and refluxing so there was no way to predict her sleep pattern. There was no way I was going out of the house without her ever. And I was perfectly fine with that, preferred it in fact. But with the predictable sleepers, I felt quite comfortable going out.