First, don't use the negative for these sentences. You want to indicate that waiting is ok before this time and not after, correct? In that case, you should use:

I can wait until 8pm.

 

I can wait (for) up to one week.

You can place "for you" after "wait" or at the end of the sentence.

"Up to" is used for a period of time and you can use it with or without "for". For example:

one week
three days
a year

"Until" is used with a point in time. Other examples:

tomorrow
10:30
Friday

If you wanted to indicate that you were very excited for something to happen and that you didn't want to wait for it to happen, then you could use the negative form "I can't wait", but I'm guessing that this isn't the meaning you want here.

First, don't use the negative for these sentences. You want to indicate that waiting is ok before this time and not after, correct? In that case, you should use:

I can wait until 8pm.

I can wait (for) up to one week.

You can place "for you" after "wait" or at the end of the sentence.

"Up to" is used for a period of time and you can use it with or without "for". For example:

one week
three days
a year

"Until" is used with a point in time. Other examples:

tomorrow
10:30
Friday

If you wanted to indicate that you were very excited for something to happen and that you didn't want to wait for it to happen, then you could use the negative form "I can't wait", but I'm guessing that this isn't the meaning you want here.