If the player before you in canasta freezes the pile with a wild card, can you pick the pile up if you have two wild cards in you hand? Do you have to take the entire pile or just the wild card on top?
No, you can't.
The discard pile can never be picked up while a wild is on top. In order to pick up a frozen pile, you must have 2 naturals in hand that match the card on top of the pile.
When the discard pile is frozen against you, you can only take it if you hold in your hand two natural cards of the same rank as the top card of the discard pile, and you use these with the top discard to make a meld.
Note that you can never take the discard pile if its top card is a wild card or a black three.