I am going to put my account on vacation hold for a bit, due to tight finances for a bit.  Will I still be able to join the discussion forums?

Yes, I have heard of many people who put their account on hold, mostly because they have too many credits or too many books to read. You can still participate!

Yep. Mine is on hold. I have around 300 unread books and the WL offers kept coming. So I put my account on hold. I didn't have much on my shelf, didn't need any credits or books anyway.  But I still post everyday.  I take it off hold when I want to post a WL book and then put it right back on hold.  Twice I forgot to put it back on hold-the 1st time 3 WL offers came in and I accepted them all.  The 2nd time-it was only for about an hour and 1 WL offer came in-I turned it down since there were 30 other people looking for the book.  I put it on my RL.  It's not like I have nothing else to read. 

If you have credits and still want WL book offers-put them on autorequest.

Yes, I have heard of many people who put their account on hold, mostly because they have too many credits

That made me laugh.  I will NEVER be in that position!