Yes, GUAVAS is a Scrabble word!

Letter values in Scrabble US: G 2, U 1, A 1, V 4, A 1, S 1.

Is it a valid word?

GUAVAS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

small tropical shrubby tree bearing small yellowish fruit
small tropical American shrubby tree; widely cultivated in warm regions for its sweet globular yellow fruit
tropical fruit having yellow skin and pink pulp; eaten fresh or used for e.g. jellies

Also: strawberry guava, yellow cattley guava, psidium littorale, true guava, guava bush, psidium guajava.