Yes. You should be able to hopefully get a feel from feedback that you get throughout/at the end of the rotation. You are almost certainly not going to get turned down, even if the writer didn't necessarily love you. If you're really worried about this, you can always ask if they feel like they worked with you enough to write you one, as this is typically the "out" for attendings who strongly don't want to write a letter for you. You can also tell them at the beginning of the rotation that your goal is to perform at an intern letter and possibly earn a strong letter, and that you would like constructive criticism to help you get to that point. A statement like that would certainly catch my interest. It would otherwise be quite uncommon for someone to decline to write a letter. (unless you ask months after the fact. Please don't do that)
It's not like there is really such a thing as a "bad" letter. It should just accurately reflect your performance, with a little fluff. For example, I wrote three residency LORs for people doing AIs this year. Person A was fine, very smart but with some issues with presentations, not a ton of drive. They'll make a good resident, probably not here though. Person B wasn't quite as smart, but worked hard and was personable. I'd be happy to have them as a resident. Person C was outstanding, saw more cases than the residents, never left my side, read about cases overnight, had great off-the-wall plans, great attitude. I really want them as a resident.
So while all three got letters, and all three had positive attributes, you can tell by how I describe them that the letters will not read the same. A letter isn't going to hurt you. But when your letter says "this is one of the best medical students I have ever worked with" or "this student would be a great fit anywhere, but honestly it is my hope they decide to remain at our program for residency" it'll catch some eyes.
What I would recommend is working very hard during your acting internship, or aways, and be cognizant of your performance. You should be killing it, or altering your performance to make sure you're killing it. We all work with a ton of medical students, and if you stand out it'll be noticed, so that should be your goal. It blows my mind that some people seem to be in cruise control on aways or acting interships, but it happens every single year.
Also note this is all just my opinion. Not everyone looks at applications the way I do, and not every program cares as much about letters. But a good letter can only help you.