Check out how many likes they have now
This is a clever promotion for quite a few reasons.
Their Facebook page comes alive with this each day Mexico wins a medal
First of all, when you are running a food outlet, any time you are not earning money, you are losing money. Between lunch and dinner time, your staff are being paid to wipe down the counter, talk to each other and stare blankly into space. It is better to use that time to promote your products without cannibalizing your lunch and dinner sales. Giving away two tacos is a small amount to pay for introducing your tacos to potentially a first time customer. This is especially important when you are a new kid on the block.
Secondly Salsa's is increasing their mindshare amongst the general public (that know about the promotion) by making people think about Salsa's every time they look at a medal count.
Thirdly they are linking customers' word association with Mexico to Salsa's so that next time you think about Mexican food, their shops come to mind.
Fourthly if they do get a nice long queue in front of their stores at 2pm, it will make people around their stores wonder what's going on. Not only is word being spread on social media, people in the immediate proximity of the stores will also notice a fast food chain that they might not have noticed before.
So what do you think?