We get a question every now and then about how to write on a poster with a dry erase marker. Our glossy laminate does this very well. In fact, we keep our job schedule board in our shop using dry erase markers on a gloss laminated poster.
Certain dry erase markers work better than others, but we find Expo black markers work best. Also, the longer you leave the writing on the poster, the harder it is to erase completely, so wipe them off when you are done instead of the next time you use them.
If you get writing that is hard to erase, use Goof-Off, a solvent available at most hardware stores to clean them. This will make your poster clean as a whistle- and it will even take off regular magic marker if you goof up and use that instead of a dry erase!