Let's be clear, there is absolutely NO foreign policy option available to the US that would satisfy its detractors. It doesn't matter if the US intervenes or stays apart from what happens, it will do wrong. For its critics offer no real options at all.
The US has previously engage in armed intervention to overturn dictatorships and to institute a form of democratic rule, and was damned for it. What regime has been more vile in recent history than the stone age Taliban, which explicitly wanted girls kept as uneducated chattels for men, and which banned music? Yet overthrowing that regime and allowing more moderate, yet Muslim forces to come to power in Afghanistan is damned and condemned. The USA was meant to take 9/11 as a moment to reflect, except for those 3,000 or so murdered in that attack. It was meant to let Al Qaeda operate freely, and indeed fold to its demands to get out of the way of it imposing its deathly will upon the Middle East. The US did provide support for Saddam Hussein in the early 1980s, as a failed proxy against Iran. That was criticised and still is, as if Reagan was still in power. Then the US overthrew the regime, and it was criticised, because dictators shouldn't be overthrown by external force.
So the US ought not to overthrow Mubarak.
Yet supporting Mubarak, a policy which, to be fair, Obama inherited, is also unacceptable to its critics. Mubarak is a kleptocratic authoritarian bully, so should get no support at all.
So should the US simply withdraw aid from Egypt and not care what happens?
No. That too would be criticised. If Mubarak remained, it would be the fault of the US for... having supported him before.
Should the US say Mubarak should go and there should be free and fair elections?
No. That would be interference in Egypt's internal affairs.
So what should the US do? Rather simply, it should ignore the vacuous hypocrisy of those who appease dictatorships they like, and look after its national interest.
That interest is to defend the security of the US and its allies. At the moment, preserving as much of the foreign policy status quo of Egypt is that. Maintaining peace between Egypt and its neighbours is paramount. A free secular liberal democratic Egypt is likely to be the best way to ensure this, but the likelihood of this happening spontaneously is fair less certain.
Democracy consists of more than elections (even if they are “free and fair”, as everybody keeps saying): it is freedom under the rule of law. That involves institutions such as an independent judiciary (which Egypt does have a semblance of), mechanisms for holding government to account after it has been elected, and disinterested agencies of public order which rely on an abstract idea of justice rather than loyalty to the ruling elite. All of this relies on the vigilance of a citizenry that has been specifically educated in these principles and in the quite complex system that embodies them.
The absence of this is not a reason to leave Egypt to dictatorship, but it is enough reason to promote more than just elections for Egypt to have a peaceful future.