This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
If you are asking "Should we include properties files in a jar?" then the answer is "Yes, probably".
If you are asking "Can we include properties files in a jar?" then the answer is "Sure we can".
But I don't understand "Do we include properties files in a jar?". Probably a language thing... I can't tell whether "we" includes you and me or whether it's you and some other people, and in any case I don't know what those other people might do. So perhaps one of those other two questions might be more practical. Would you like to clarify?