Re: What tense should be used in the sentence?
It would also be correct without "would".
I decided to hide, and wait and see if anyone entered the house after I left.
One thing: it is potentially ambiguous as it's not clear whether:
- you decided, after you left, to hide and wait and see if anyone entered
- you decided to hide and wait and see ... if anyone entered after you left.
It's not an important ambiguity but it's still there.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.