Upgrading from Snow Leopard (10.6.8) to Mountain Lion

So I purchased Mountain Lion online and received the redeem code from Apple. I've redeemed the download for Mountain Lion but have been having issues trying to even initiate the download. I've gone into system preferences and turned off the computer's sleep mode to prevent the computer from going to sleep during the download. When I click download, the App Store seems to load for a second and then it just goes back to saying download (as if I never pressed the button, or at least that's what it looks like). I have gotten it to start downloading once (as indicated by the icon that appeared in my dock), but about mid-way through it failed and said I had to retry.

I'm upgrading from Snow Leopard (v10.6.8) so I don't have launchpad. I'm also limited in my ability to get fast internet (I have to go to a coffee shop to get decent internet where I live). So I guess a couple questions:

1. Is there a minimum internet speed requirement for downloading Mountain Lion? (If not, I'm willing to wait at the coffee shop even if it takes a while)

2. If it isn't necessarily an internet speed issue, could it possibly be downloading somewhere where I can't see it download? (although I this seems unlikely as I have had the download appear in my dock on at least one occassion)

3. Is there anything else on my end that might be causing issues with the download that anyone can think of? (I've called apple a couple of times already so I just wanna make sure there isn't anything glaring that I might be missing before I try to call them again)

If there is any other info that might help diagnose the situation, let me know and I'll try to describe what's happening on my end

Thanks!