Don't laugh, but I took both even though my DH & I packed as light/small as possible. My husband & I each took a very small compact umbrella as well as plastic ponchos that folded down to nothing (couple sq inches at max.) We were adopting 2 babies and I wanted to make sure we could keep them dry -- keeping us dry was an extra bonus, heh, heh.
You can usually find very small umbrellas and tiny fold-down plastic ponchos at both the Bulleye store and the yellow smiley face store (don't think I'm allowed to list names, but that should give them away.
)
Best of luck and have a wonderful trip.