What is colitas in general english?

It's a slang term for drug use.
Urban Dictionary: colitas (http://www.urbandictionary.com/define.php?term=colitas)

I remember an old song:
On a dark desert highway, cool wind in my hair
Warm smell of colitas, rising up through the air
Up ahead in the distance, I saw shimmering light
My head grew heavy and my sight grew dim
I had to stop for the night