Can I use whipping cream or half and half for making panna cotta?

Yes, whipping cream is better. Here is a really good recipe that I've made probably 10 times now. You can substitute the vanilla extract with 1 whole vanilla bean if you want. Just make sure to add the beans after cooking, but boil the pod with the cream mixture.
http://m.allrecipes.com/recipe/72567/panna-cotta


In fact, I'm using it as part of a contest entry at my local farmer's market!

Certainly! What does your present recipe call for? If you are going to sub heavy cream, simply be aware that you should probably boost the gelatine content. For heavy cream or half and half, the conventional ratio is 3/4 tablespoon of gelatine to 16 ounces of cream.

Waist. I really need to stop answering things with my phone. ;)

I use whipping cream. The higher the fat content the better. Might not be waste friendly, but any dairy based desserts have a better mouth feel with high fat content dairy.