If I am connected to a main computer which is DSL connected, and I am on a wireless network through this computer-

Will all the others on the same wireless network have the same IP address?

NO.
There are two sort's of IP address, Public and Private.
Now your home network likely runs 192.168.x.x this is translated by your DSL router into a public address (I won't post it here) for example 10.20.30.40, this is your public address that the outside world can see.
This public address is assigned by your ISP and changes occasionally.

If you want to know what your public IP is try this : InternetFrog.com: Network Tools, Internet Speed Test and Website Tools (http://www.internetfrog.com/index.asp)

Thanks...
I was just wondering if someone else signed in from any of these PCs, if it will seem like I had an alias!:)

P.S.I love the frog eyes on the link you gave... ;)

Basically YES as you would appear to be coming from the same address.
There is NO problem with this as long as the other account isn't used for abuse.
My wife and I share a connection and there are a few others on the site as well.
Bare in mind I don't trawl the logs looking for IP matches, only if there is cause for suspicion.

;)
You can never be too careful...
We never know what sort of worms,snakes and other crawlies are slithering around internet sites.