I believe I read somewhere on the forum that your hands were getting sore from practising Rach 3 and other pieces. I would just give it a break for 3 days. You can still learn about the piano in that time e.g. by studying the score, practising in your head, listening to recordings. If you want to give a certain passage a go, do a bit of practice on the bad piano, but don't overdo it .
Whilst I wouldn't commend crap pianos as a general usage, there is a surprising amount one can learn from one. Make it sound good. Or at least try. You may be surprised - either by what it can do, or by what you can then do on a better one.
So my question is, should I practice on this thing, or just give piano a break for a few days. To get back to my upright.
If you have to ask then the answer is YES
I am staying in another household for 3 days. That's all good, but my problem is that the only available piano is a slightly out of tune pianola (Brinkerhoff). Most of the bass notes need replacing (the further down you go, the worse it gets) and half of the really high notes either don't work at all or you can barely get a sound out. There are about 4 sticky keys in the piano. The piano has one of the strangest sound ever, like a honky tonk type sound. The room I'm in is echoey, so it's really hard to play forte because the sound seems to go on for ages (sustain pedal or not). Paired with the echo thing, it's also just generally a really loud piano, which makes it almost impossible to play softly, no matter how light I touch it.So my question is, should I practice on this thing, or just give piano a break for a few days. To get back to my upright.