I was going to post something like this a few days ago since I seen another solution on another site. When in a friends town tap the Town Hall, Moe's Tavern, Police Station or Springfield Elementary because you can still vandalise their towns but still not tap on other buildings. The cash, xp, donut or friend points don't appear when you vandalise the buildings but you hear the sounds and the actions register in their town. I only wish I found this out 6 weeks ago. Credit goes to Patric on tstoaddicts.