Cards are cheap, but your trip is not. If this is one of those once in a lifetime trips, I'd recommend having an alternate backup method regardless of how many cards you take. You could have a dozen cards but a set of photos will remain on one card at all times. If you're shooting on 8GB cards, that's hundreds of photos on one card.
For my gigs, I purposely stick to 4GB cards so I can backup as I go. Think of it in terms of film, back when you had to lug around dozens of rolls of film until you could get them developed - One lost roll could be irreplaceable, same with cards. Note I'm not talking about cards failing. I'm talking lost, stolen, oops moments.
If you don't want to take a laptop, you could consider a stand-alone data storage device. A couple of non-fancy models are around $150 and fit in a pocket while still providing you enough storage for a month long trip. This way you can keep images on the SD cards
and back them up to the storage device. Two backup methods, just in case.
Digital Foci: Photo Safe II Portable Picture Storage
How about 250 GB of storage for $130?
Digital Foci - Photo Safe II 250GB Stand-Alone Data - P19-250 -
P.S. As far as fear of robberies, wear jeans and use your front pockets. Tougher to get into. Best of luck on your trip!