Actually the site is not too bad. Have patience Grasshopper. Gramps pointed you in the right direction.
I believe the answer is yes. Go here for more info: http://prepaid-phones.t-mobile.com/prepaid-plans .
If you have the Pre-Paid $30/month, Unlimited Web and Text with 100 minutes Talk, it would appear that you can purchase for $10 the International Unlimited Talk and Text plan. Make sure the countries you are going to text are included.