Check out the following threads on the Android-x86 Google Group. I have never done SMS with Android-x86, but here is a synthesis of some things from the group. I am guessing that it cannot be done. Also, you should see this SO question.
From Telnet connection to Android-x86:
...should be able to connect to "telnet 192.168.1.XXX 5555" and send "sms send 555123456 SMS_text_here" to simulare an SMS, but the telnet connection is not working....
No responses.
From android x86 telnet connection:
... So I was wondering, are there in a plans to make it more as an emulator stuff for developing purposes ? I mean telnet connection simmulating sms'es...
No responses.