Move out of unanswered to give others a go !!

When travelling in the USA what would be the most cost effective method of using a mobile phone? Presumably using my Blackberry for telephone calls and internet use will be expensive from my current provider (orange). Should I buy a pay as you go sim in the US? What about the sim provided with the pre-loaded Escape cash card? Is this sim cost effective? Or should I avoid using a mobile phone in the USA completely and use pay phones. For internet access, could I use wi-fi hotspots at places like Starbucks for free or will I incur charges using my phone access from here too?