By PDA do you mean Palm device? If so I did a bit of research on wireless Internet for Palms and also used them to see if they were worth the $600 to $800 price (includes modem). The answer that I came up with is no.
A couple of hundred more dollars buys you a nice laptop. With that you can access anything worth accessing.
AT&T offers a $5 a month wire line connection which can be plugged in anywhere in the country and pointed to the local access number.
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