I know that you must buy the unlimited Data plan for $30 to activate this phone. I know that gives you internet where ever you go, but does that $30 date plan also include unlimited texting?
No it does not provide texting at all (Not "texting" as you now think of it - meaning SMS texting)
There are a LOT of alternative ways to send messages from any Android phone (but if you want to send a message to another cell phone that does not have the capability to use one of the IM clients, you have to use SMS) - There is google talk, yahoo messenger, msn (shivvers) etc. You can also request a Google Voice account, install the Google Voice app to the phone and send/received (SMS) text messages (but not picture messages yet) from your Google Voice number. The reason you might want to use Google voice to do your texting with is that you can send "normal" text messages to "regular" phones. You can also log into your google voice account to send and receive message to/from cell phones right from your computer. Getting an invite for Google voice could take 1 or 2 weeks. You can get an invite by going to http://www.google.com/voice
(Voice adds SOOO much more, but your question is only about texting )
250 text message/month is an additional $5/month on Verizon if you don't want to go the Google Voice route and/or if you want to send pictures. (Keep in mind you can also send pictures and messages through email on the Eris, or any other Android phone.)