From what I'm reading knitting needles are often confiscated on flights returning from Mexico. People have better luck with wooden shorter needles, but they too have been taken. I have my Probability Cowl on wooden Webs interchangeables. That's not the most exciting project, but it might be worth trying. I can unscrew the needles and put them in with my pens/pencils. The cable is short and hopefully won't cause a problem.
As I write this post I've been searching for projects. I downloaded High Seas, beautiful stole/scarf that reminds me a bit of Hanami. I think it will look great in the Madelinetosh Lace I bought at Knitty City in December. I'll wind it up and stick it in my bag. It will use the same needles as the cowl and strangling vine so I can bring a few cable knobs and just switch needles. Now I'll have a lace project that will make me happy!