Yes you can. They do sell out rather quickly though.
We were considering getting one last August but decided not to, and in my opinion it was a good choice.
The party isn't very long and we spent most of the time doing the slides, wave pool, raft rides, and lazy river. We had a lounge chair and rarely found ourselves there. The night was over before we knew it.
Now, we always get a cabana on our water park days. But it's great for us for escaping the crowds, escaping the sun, and taking nice half an hour breaks here and there. None of which will be relevant nor needed during H2O glow.
Your choice obviously. But if you do want one, I'm pretty sure that the 60 day rule will still apply.