Swallow is one of most YMMV things there is. Just think of it from the girl's perspective, swallowing multiple loads a day from different dude's is a recipe to be out sick for a day or two which means less earning opportunity. Its usually not a problem to swallow once or twice if its not a fast food brewed load, but the comingling of different sources from multiple people can be bad for the stomach.
Best you can do is eat nice for the week, have a cup or 2 of pineapple chunks the day before, ask before you pop and hope for the best