using an unlocked sidekick with at&t-help!

so i have at&t as my provider and i have razr that i've dropped soo many times and the screen is cracked and i've wanted a sidekick for as long as i can remember, and i found one on ebay from a seller who has only good reviews. this may be a stupid question, but i want to clarify before i spend my own money on a new phone. so the question is will i still be able to text with the unlocked sidekick? i read in a different thread that you can still use the calling device but no browser, aim, or anything like that (i don't want that anyways) but texting wasn't mentioned. i text all of my friends all of the time so this is kind of a selling point for me. does anyone know if i will still be able to text if i buy the sidekick?
thaaanks.