J.C.
For my 30th (I was pregnant) I had my hubby take me on a cruise to Mexico. We left from Long Beach and went to Ensinada and back. We didn't plan any shore excursions because it wasn't in our budget, turns out we didn't need them. A cruise on a budget is a ton of fun!
We spent $250 per person, we got close friends to watch our other children and off we went. You can get great last minute online deals.