Most of the postings are RUBBISH and full of EGO ...

Rubbish reaction is unfortunately caused by some very lazy people, not willing to carefully read a datasheet containing more than 20 pages. They just post a question, and let others do their work. And when it seems to us, that someone hasn't read datasheet then he will get just this reaction. But: Very most members are very nice, hardworking and all the time ready to give help. Please don't forget this!

To your question:
For mcu output 56kb/sec isn't fast, at all. Time per bit is much more than 1µsec! But output of MCU settles in about 10nsec (depends on capacitive load). Assume you use slowlier open drain output feature. Further assume using 1kOhm pull-up to 5V. Then having a capacitive load of 10pF (stray capacitance) results in a rise time of 1kOhm x 10pF x 2.3 = 25nsec. So, even if you drastically increase pull-up resistor speed is not a problem, at all!
To level compatibility. '232 chip accepts 2.0V for input logic threshold high. Then, even working without pull-up to 5V there's enough noise margin. You only should have guaranteed that power supply decoupling is adequate (at least 100nF X7R directly at Vcc pin of mcu) and to use todays PCB design techniques, like massive goundplane, etc. But that is standard, anyway.

Bye,
Kai