Canasta opening with jokers
No.

Any valid meld in Canasta needs to have at least 2 naturals in it, so wilds by themselves are not enough.

From Bicycle:


  A meld is valid if it contains at least two natural cards of the same rank - aces down to fours inclusive - and not more than three wild cards. Jokers and deuces may never be melded apart from natural cards.


Note that there is a variation of this rule that is seen in some places; according to canasta.net:


  However, there may never be more wildcards than natural cards within one meld.


In most situations, these 2 rules work the same way; they both mean that a meld of 3 -7 cards must have at least as many naturals as wilds.

The difference is that one of the rules allows you to add a 4th wild to a Canasta that has 4 naturals and 3 wilds, while the other does not, but this rarely could matter, as you can likely just add that wild somewhere else instead if you need to.