Yes, yelp is a Scrabble word!
...and is worth 9 points in Scrabble, and 10 points in Words with Friends
yelp
Verb
1. Bark in a high-pitched tone
Noun
1. A sharp high-pitched cry (especially by a dog)
What Scrabble words can I make with the letters in yelp?
3 Letter Words
2 Letter Words