AT&T has announced an Interantional iPhone data plan.
If you must use your iPhone during travel and need access to a data plan, check out this AT&T iPhone world data plan that gives your 20MB for $25/month. Participating countries include Canada, China and Mexico. Overage costs you $0.005/KB and use outside those 29 countries costs $0.0195/KB. For more information, please follow this link.