Learning DB2 without a local install
I don't think you can avoid a local install. I'm not aware of any online sites (e.g. SQLFiddle does not offer DB2).

In addition to the book you linked to, I can highly recommend the "DB2 SQL Cookbook" as well: http://mysite.verizon.net/Graeme_Birchall/id1.html

And don't forget the official manual: http://pic.dhe.ibm.com/infocenter/db2luw/v9r7/index.jsp