I have been wondering if you can breed the vintage monster collection ( Panda, Fire Lion, Firanda, or Turtle.) are they available for breeding?

Yes they are, unless the combos have changed they are:

Fire Lion [c] - nemestrius/shallinar -
Turtle [c] - griffin/rofl -
Panda [c] - Firelion/Firanda or Yndra/ROFL
Sea Lion [uc] - vodyvoy/granuy
Shock Turtle [uc] - thunder eagle/donaturtle
Firanda [uc] - fire lion/turtle

Requirements actually are:

• Panda = Fire Lion + Firanda (5%) OR a 1% chance by breeding any 2 legendary monsters.
• Fire Lion = Turtle + Panda (5%) OR a 1% chance by breeding any 2 legendary monsters.
• Turtle = Panda + Firanda (5%) OR a 1% chance by breeding any 2 legendary monsters.
• Firanda = Fire Lion + Turtle (1%)

Sealion and Shock Turtle aren't in the Vintage Secret Collection, they're just breedable like normal.