Heck yes, you should!
1) It helps establish if you have chemistry. If you really like someone, you shouldn’t let outdated dating rules get in the way.
2) If you communicate beforehand, it ensures there are no mixed signals or unclear expectations. If things are getting hot and heavy, and it starts to look like first-date sex is in the cards, you need to ensure you guys are both on the same page.
3) You get to, uh, have sex. If it feels good, right, and there is enthusiastic and clear consent, it’s kind of hard to find a downside.
Eh, maybe not
1) You might lead the other person on. If both partners are looking to have fun, hook up, and part ways, then that’s one thing. But if she’s looking for something serious and you’re not (or vice versa), then that’s another story altogether.
2) You might do something you’re uncomfortable with. If adrenaline (and alcohol) are flowing, that ups the risk of you doing something you might later regret.
3) First-date sex can be pretty terrible. If this happens, you might be more likely to write the other person off (or have your partner write you off), when in truth, all you guys really needed was more practice.
So what’s the ultimate takeaway? If you’re open and honest about what you’re looking for, then you have no reason to feel regret.