A lawyer told me you could use any name you wanted to, so long as it was not to deceive or defraud.

Correct. While looking up something else I quite by accident stumbled across a case noting thus (with 11 citations):

... under the common law (which is recognized both by Illinois and by the federal courts in this regard), a person may adopt a new name without resorting to the courts, and may even use his birth name again after having adopted a new name for a period of time. A party may properly effect legal process under any name so assumed. Indeed, a person who is known by two different names may use either name in legal process without affecting its validity, even if the name used is not his "true" name.