Most women do lose weight from the top down... it's the natural way of things. During our child-bearing years, our bodies are designed to horde fat around our mid section/hips and thighs just in case we need it for having babies.
What a cruel trick God plays on us!
But eventually, you'll lose from the middle too.
Like others have said, during that first month, you should notice more loss from your face, neck and upper body. I'm 11 weeks out and still wearing my old size 20 shorts, but then again, I don't like tight clothes. I kinda enjoy walking around in my baggies! It's nice to feel comfortable once again! You'll feel the same way.
If you do decide to go shopping before your trip, make sure you go RIGHT before because you won't be able to guess your size.
Have fun on your trip! And remember, you'll still be healing and getting used to your new tummy and body, so take it easy!
I'm such a mother hen.
Traci