Welcome to HealingWell!
I've never taken Flagyl or Saccharomyces (or even Welchol), so I can't really help you there. But, I can tell you that sometimes it takes a little while before the D stops. Your best bet is to keep taking mass amounts of probiotics. I've never read anything negative about
mixing probiotics... Maybe you could take both Culterelle and Sacch. I'm pretty sure I've read that taking probiotics for at least 2 months after antibiotics is the way to get back on track.
Actually, lots of IBSers are on probiotics indefinitely. I am. I love them. I take 2-3 different types a day.
I hope others come on soon to give you some input. It would be a shame if you couldn't go on your vacation. Maybe you should call your doc on Monday if you're not any better.