Connecting multiple arduino

I doing a project of measuring multiple weight simultaneously, in which there are multiple hx711 connect to their respective load sensor. I searched the net and forum for connecting multiple hx711 to a single arduino but no fruitful result was found. So now i am considering to a individual uno for each hx711 and then connecting thats unos to mega to transfer data(float) . Mega would pass data to computer via serial. I should be able to communicate with atleast 7 unos via mega. For communication between arduinos i am confused regarding method to used whether i2c or spi or uart or individul software serial. Easiest would be i2c but i am concerned regarding its speed i need to updated data of all uno within 1- 1.5 s. Would i2c be okay for that speed. Or suggest any other method.

Multiple HX711 on one Arduino

I don't see why you can't have 7 load cells connected to a single Uno.
Each HX711 board is only using two digital pins (analogue pins are also digital pins).
I've seen sketches with two instances of the HX711 board. Not sure how many the library can support.