Personally I use Google Voice for SMS on my tablet. I am not sure if GV is rolled out in your area or not, but there are other SMS apps in the Play Store. Viber is another option.
Musing: The link is helpful, but not specifically for my query ( thanks - it was helpful overall though!)
Frederuco: Unfortunately, Google Voice is not going to happen in Australia any time soon - our mobile prices are ridiculous compared to most countries ($20 a month to lease a virtual mobile number, for example).
All I want to know is if SMS (real SMS - not fake 'free SMS' apps) is possible on a tablet by the use of a dongle. It seems that this is an uncommon request.
If anyone else has some ideas, please let me know. Thanks!