I like the first one, but was also thinking of a few others (maybe you can have one of those digital signs that changes!)
RABIES TESTING... APPROACH AT YOUR OWN RISK
UNLESS YOU WANT TO BE PULLING A CART, GO AWAY
OWNER SO BROKE, DOG HAS TO WORK
NEED GAS MONEY, DOG IS GETTING TIRED
GIVE MONEY, NOT ADVICE
THIS IS WHAT YOU GET WHEN YOU PUT THE CART BEFORE THE HORSE
DOG'S NAME IS "MACK" OR "FREIGHTLINER"
KEEP BACK 200 FEET... DOG HAS NOT YET LEARNED HOW TO PARALLEL PARK
STILL WAITING FOR DMV
AND MY FAVORITE..... JUST GO AWAY!