I only smell propane when I walk by the furnace. Does this mean there is a leak?

Possibly. I would get a professional to check it out ASAP. Better safe than sorry. You really should not smell any odor resembling rotten eggs indoors near your furnace if everything is in perfect order. I have a gas furnace AND water heater next to each other and there is NO gas odor around them. A disclaimer here being "Gas" odor really means the additive to make detection by the human nose possible because both Propane and natural gas themselves in their natural state have no odor at all.