OK, supposing you're rooming with someone...
Suppose you're rooming with someone, and the room is on their credit card. You're getting in at noon; they're getting in at 8:00 p.m... Do you have to camp in your car, guarding your belongings from roving thugs with bricks* or is there a way to make sure you can get into the hotel room before your roomie and her CC shows up?
*not implying that Pittsburgh is full of roving thugs with bricks or anything. Just making a joke and failing miserably 
Two choices:
1) If your name is on the reservation, you can check in with your credit card (NOT your debit card!). You do not need to check in with the same credit card that was used for the reservation.
2) You can get a credit card pre-authorization form from the hotel. Your friend can fill it out and give it to you. It essentially says "Hey, I'll give you my credit card when I arrive, but in the meantime, let my friend here use it." You can get one by sending an email to jaime.andrade^at^westin.com. Tell her I sent you.
IF YOU MAKE NO ARRANGEMENTS, then, yes, you're stuck waiting for them.
If the room reservation has been updated to include your name, and you have ID, that's a different story. If this is the Westin and they're doing what they've done- or another hotel with the same policy- then you need to present a credit card when checking in. I secured a room at the Westin with a big cash deposit in advance including extra to cover "just in case." My roomie arrived before me, and had to present his credit card, which was never touched because the money I left secured the room for any practical expense.
If you don't want to present a credit or debit card- or are UNABLE to- then you still have one option. If the reservation has your name on it, and you have the reservation number, then you can present your name and reservation#, and the hotel- since you proved you're checking in later- can store your baggage until later. Tip the person putting them away, make sure your name & address is on each piece, and find out exactly where to show up with your ticket to get it back. (Tip the other person, too.) That means you have until 8pm to do stuff without checking in. Go for lunch and dinner, hang out at the Zoo, see if ConOps could use a helping hand, and so on. Basically, all of Thursday and PROBABLY from noon on Wednesday, there's places set up. If it's Wed and they're NOT set up, go to ConOps and volunteer to help set up the Zoo.
Then you know when it's set up, because you're one of the people setting it up. 