were should i go to lvl im a lvl 54 and i am looking to lvl to 58 were should i go to lvl up fast  should i do dungens or just grind

IMHO, go questing. Un'goro if you haven't finished it, and afterward Felwood, Azshara and Winterspring.  Then go to Western Plaguelands followed by Eastern Plaguelands.  Still a lot of good XP to be gained in the Plaguelands.  I stayed there until I was 60 and then went to Outland.  I still left a lot of quests behind in EPL even though I stayed an extra 2 levels.

dougeons and questing cuz grinding takes way to long when your a high lvl

Grab all the quests for an area, includinbg those for the dungeon, then grind to the dungeon, back from the dungeon.  Most of your quests will be done with some "small detail work" to finish a couple off.

That really cranks out the levels, I got 4 in a weekend when I was in the L30's doing things that way.

by far quests bec grinding normally takes twice as long to lv and for dungeons u either need a group which shares exp or go to a way low dungeon which doesnt give any exp. 

Def. questing but Grind on your way to the quests. that way you knock out both "questing" AND "grinding"...makes sence right.

you are grinding, but in the same time, you are picking up items that you need for quessts...

i found this to be most effective for lvling. i have only had my warlock for about 2 1/2 weeks and I am a 37. ""(just shy of 38)