Will I be able to get my lvl 20 pet back from the menagerie?

I've just started checking out the menagerie. Interesting idea. I'm tempted to start collecting pets. Gotta catch 'em all!

I have a level 20 pet. If I put it in the menagerie, will I be able to get it back? I've heard people complaining that they've put their high-level pets in only to be able to recharm level 5 versions.

If you talk to that trainer just behind the dude who you give your pet to, you can ask to spawn an animal up to level xx (the one you handed in) from any evolution.

Once you put any pet in the Menagerie it's level 5 counterpart will wander the grounds, free for you to tame should you ever want to.
However, to get a higher level or different evolution of a pet you've placed in the Menagerie, you need to talk to Wynn, the zaishen training person thingy... she will give you a choice of different levels and evolutions, providing you've already unlocked (in PvE) or purchased (from Helena, the zaishen keeper person thingy) the level/evolution that you want.

So... short answer, yes.
When you put a level 20 pet into the Menagerie, you can tame it again, anytime you like.

She - named after our very own Wynthist, Auction Admin extraordinaire, dont'cha know