I eat out a lot. More than I should, I'm sure. I stick to the basic Paleo rules when I'm out (GF, DF, no beans, no grains, etc) but I'm almost sure 99% of the time there are some oils slipping in that aren't considered Paleo. You can stick with cold foods and stay pretty safe, like salads, etc, though if you care if your meat is grass fed, etc, you're not getting that either.
It all depends how strict you want to be. If you do, don't eat out, it's that simple. Some of us can't avoid it (or perhaps don't want to?) and so we make allowances. I cook for my kids and my husband and I at home most of the time, I work full time, it happens and I don't stress about it.