I'd think the better question should be about how you'll be able to manage the memory cards while on holiday.
For example: Do you have some sort of system for transferring picture files to a portable storage device?
If you're planning to take a portable computer with you, you can easily transfer picture files to the computer with the use of a USB card reader. There are also storage devices made specifically for offloading camera media cards.
If you're not planning on toting a portable computer or a dedicated storage device, additional memory cards are certainly very inexpensive nowadays. Seeing as SDHC cards are terribly inexpensive anymore, I'd just load up with a few high-capacity cards before you travel. 4GB and 8GB cards are incredibly inexpensive here in the States, and as whiteflyer mentions, you'll pay a huge premium for the same thing overseas. An inexpensive SD/SDHC-to-CF adapter can cut your costs, if your camera uses CF; I grabbed an SDHC-to-CF adapter for around 14 US dollars.
2GB, 4GB and 8GB cards currently tend to sell for less per GB now than 16GB and higher-capacity cards, so it may be more economical to purchase a bunch of 2GB cards as opposed to a shiny new 32GB or 64GB card.