I'm assuming you are invoking the Equal Protection Clause, in that they are spending money on some but not others. There are a number of cases which say that the government can spend money as they see fit, as long as the class of people being advanced, hindered, are not a protected class (in thoses cases there must be a state interest: rational basis, compelling interest, etc). Non-downtown people are not a protected class. Honestly, if they had to be "equal," it's impossible, they could never do it, and our government would cease to function.

I think Downtown is a huge economic benefit for the city/county, and it could be a lot nicer if more people live, worked, and invested downtown.