I've had my pouch for a pretty long time, and I certainly enjoy eating celery. After your pouch is functioning you're likely to have a relatively unrestricted diet. You'll only know if you can't eat things by trying them (preferably in moderation at first).

I don't know who told you to avoid celery, but I eat it all the time with no problem.  In fact there isn't a raw fruit or vegetable that I don't eat because of my jpouch.  You might not be be able to enjoy these foods immediately post reversal, but in time you should.  When introducing foods again, eat a small amount and see how you do, if it's not comfortable, try it again weeks later.

Sue