Why would you not bring your Medela? I've brought my PISA on a couple trips, airplane included. I just carried it on so nothing would happen to it.
I've only traveled by car, but always brought my pump with (until my latest trip). If you need to use your pump each day, it's going to take longer to pump with the manual (you'll have to do each side individually, obviously) and from what I understand they usually aren't as effective as the electric so you won't get as much milk which could impact your suppy. Although, I've never used a manual pump, so I can't speak from experience.
On our last trip to Buff I didn't take my pump. I had L with me so I nursed him and have stopped pumping at night on weekends. It was 5 nights I didn't pump and now I'm having major supply issues (may also be due to the fact that I've been sick). Good thing I have some milk in the fridge and we have just 1 more month to go to our 12 month goal then I plan to start weaning anyways.