Whenever I get into a dungeon where it's my first time, I always make sure to look up a quick guide to get a general idea, but then I also let the group know it's my first run through, but I have looked at a guide and if they have any tips/info to let me know. No one in any of the groups gave me any grief, most were ok with it and explained things as we went along.

So I'd have to disagree with OP's statement, be open and honest about your experience in the dungeon, and if you don't know the fight they'll explain it to you instead of letting the group wipe or letting you die because of lack of knowledge of the fight(s).