Neither Czechoslovakia or Hungary are big enough for citizens waging a long-term guerilla war against their communist governments, without these resistance movements being eventually crushed. Even if you had new resistance movements popping up every other week, like mushrooms after rain, they would achieve nothing even if they stooped to large-scale terrorism and sabotage.
First reason why they'd fail: The government, in control of all the media outlets, would gain incredible propaganda ammo. You might even see anti-communist efforts, including those of peaceful dissent, seriously undermined compared to OTL.
Second reason why they'd fail: Czechoslovakia and Hungary under communism were fairly militarised states, as well as having nearly all-powerful law enforcement agencies. These have all the country' resources at their fingertips and are given priority by the government to keep order at all costs. Do you think a bunch of under-equipped guerillas could keep fighting minor victory after minor victory against these guys, for decades on end ? Yeah, they couldn't. Forget about NATO or the CIA or whoever supplying these guerillas to stick it to communism. It would be diplomatically too risky, and economically/militarily ineffective.
David also made some fine points on Tito's Yugoslavia not supporting the overthrow of communism in central Europe, as he feared the overthrow of his brand of communism in Yugoslavia, and was also opposed to resistance against communism on principle anyway.