don't know how well it works but i've managed to use
Free Text Messaging - Send and Receive Free Text Messages - Text'em for text mesages. It works from computer also, but you can text people to their phones as well.
I mainly use google voice text message, I got an app that lets me get to google voice for calls/texts on tp 2
on both, I cant say much about international fees though, but why not use a chat program for just texts? Fring works well on windows mobile and lets you access multiple platforms