is there a portable printer I can use with ipad 2

None of this is a real solution. no adhoc no airprint stuff...just a bluetooth certified printer (Zebra imz320) and an app called Mobi Print.

How do you print on 8.5 x 11 paper with the zebra imz320?

well if you use the mobi print it will scale the PDF to fit. By the end of the month I have heard Zebra will have a 4" wide BT printer working as well.

I found a working solution.http://www.brothermall.com/Mobile-Printers/Model/PJ673/Overview.Brother has a mobile printer only for the ipad that prints over adhoc. They sell car adapters and ac adapter for any situation. Since it just came out there is not many videos about it and it has a $500 price tag. This is a video for the previous cheaper model https://www.youtube.com/watch?v=gQwoxpDD6dI and how it works. And I also found another video of the actual 673 (ipad model) https://www.youtube.com/watch?v=KVp77vT3VaU. The brother website says an app must be used to make prints. I have just emailed the company now to see if the printer is compatible with embedded print options on other apps.

I'll hve to check that. Brother app out. Although, we have been testing adhoc with zebra mobile printers for years and the reliability on the adhoc is not very good. I still think getting a zebra imz320 printer with native Bluetooth support will be your best bet. The brother app offers no document hand eking to get print jobs quickly into the app. For anything with speed or 1 click print you will need mobi print

HP has released the HP 1200w NFC mobile print adapter. This allows you to use the HP 100 or HP 150 mobile with your iPad. Most importantly it uses the native AirPrint protocol, so you don't have to mess around trying to get a blue tooth printer working with your iPad. It also allows you to print 8.5 x 11 since it is a full size printer.

Here is a setup video: https://www.youtube.com/watch?v=9zVfCpT4X84

The new Brother PocketJet 7 is 100% AirPrint compatible, small, battery operated and does not need a network or any other device to print.

It prints directly from the iphone or ipad. Check it out at http://www.brother-usa.com/mobile/Mobile-Printing/#.VsOpfPkrKUl

The specific model is the PJ773 printer.