Should I roll for Quetzalcoatl

You would have only a 22% shot at landing her in the Babylon banner. Plus, since she is on rate-up with Enkidu, you would have an equal chance of summoning him. In fact, since the odds for Quetz overall are just 0.4% out of the total 1% chance for any SSR, you are actually more likely to get any other servant possible than her.

I can't say if you should or not--that's up to you.

She's a pretty good servant and in my opinion the best rider in the game, some people may disagree but she is at least par a par with ozy as they do almost the same but different rolls in the party. I really recommend rolling for her.

Roll if you want her, She is really powerful (she is my main ST Rider) and one of the best Riders in game.

She will have a solo rate up on the 9 Million DL Commemoration Summon (NA version could be less DL) around May I think is a better option wait for her solo rate up.
https://fategrandorder.fandom.com/wiki/9M_Downloads_Campaign

If you want her, sure. Gameplay-wise, she's incredibly solid. Good survival, buster up, NP charge and star gather. Quetz has an incredibly diverse kit but doesn't lose any of her focus as a result of her diversity. Easily one of the best damage dealing servants in the game right now.

If you're asking if you have a good chance of rolling her, that is completely up the mercy of the gacha. People have spent over 900 quartz trying to get their waifu and didn't get even one 5-star. But good luck to you, regardless.

She's a good servant to roll for.

I wouldn't roll in a banner featuring several servants though.