Chanel West Coast, Lexy Panterra Urge People to Stop Peeing in Coachella Crowd

Justin Bieber's a main draw for fans at Coachella this year ... and Chanel West Coast and Lexy Panterra really want people to go to the bathroom at a port-a-potty before the show -- not on the ground during it!

We caught up with the stars at the Grow & Glow festival by Victoria Jancke near the main festival grounds Friday ... and we had to know what they were most excited to see at this year's event.

Chanel immediately says the Biebs ... remembering him from when he showed up at Rob Dyrdek's Fantasy Factory more than a decade ago -- and complimenting him on the direction his career's gone.

Lexy says she and Justin almost got into a fight once -- unclear what exactly she's referring to here -- but, they're cool now ... and, she thinks a headlining Coachella spot is exactly what he deserves.

However, Lexy admits she has a concern for Bieber's show ... fans will be waiting around all day for it -- and, she's already seen some on Coachella weekend popping a squat and relieving themselves.

This is especially problematic for Lexy, she explains ... because she often sits before shows -- and, she'd prefer to avoid a literal interpretation of "On Golden Pond."

Chanel smiles and politely just nods along ... but, it seems clear from her expression she knows exactly what Lexy's talking about.

We also got the pair's makeup and energy tips for the long weekend ... watch the clip all the way through for all their advice.