'Would I have the right to start a party (even if it was capitalist, considering you can start a communist party here)?
There would be no parties in communism. Rather, we'd either use direct democracy or demarchy. And I doubt there will be many capitalists (thinkers, that is) once communism 'gets going'. Do you see any feudal-ists in the US or Europe?
'Why can't I own land, why isn't that a freedom?
The only reason to 'own land' under capitalism is to make money and thus survive. Well, we don't need to 'make money' in communism. Once its material base disappears, so too will the concept of 'landowning'.
You should ask them: "Is owning a slave also something you'd consider a 'freedom?'"
Well, the material incentive for owning a slave is gone (that is, feudalism is gone).
'Would I have the right to disagree with the government?
Certainly. If a commune is using direct democracy, disagreeing with the government is simply part of governance itself. If we use demarchy, then one may not only disagree with a government, one may also, if one has a majority, get the government replaced.
In communist society, any government is subordinate to the people. Not the other way around.
'Would I have more than one party to pick from at the ballot box?
There would be no 'ballot box' for candidates. See above.
"The only church that illuminates is a burning church"--Buenaventura Durruti