I don't have a juicer but I have a vitamix which pulverizes stuff.
If you are having trouble with celery and I do as well, I'd suggest a couple things:
1) smoothie with apple, celery and ginger. Add anything else you'd like as well, lemon juice goes well and you can add spinach or kale.
2) Smoothie with frozen grapes, celery and ginger. I actually got this out of a raw cookbook for 'gingerale' and it is really good.
Overall I think ginger is a strong enough flavor to counteract and complement celery. If you don't like ginger, well then thats a whole different issue