First try to understand the function of ALE. ADC0809 is composed of a SAR type converter and it has a 8-->1 multiplexer at its input.

The Multiplexer:
To select any particular input (the one to be digitised) you should provide a 3 bit number so that multiplexer routes that particular I/P to its O/P. However there is a requirement of ALE signal as well along with this 3 bit number as stated in the datasheet "The address is latched into the decoder on the low-to-high transition of the address latch enable signal.

Now the ADC requires a certain amount of time to convert the analog signal to digital. During this time, the analog signal should not change. This time will depend upon the frequency of the clock signal input to ADC. (at 640KHz, conversion time is approx 100us).

And you are going to drive ALE with a signal of 469KHz. This corresponds to a time period of 2.13us. In this case, your ADC will see a change at its input at every 2.13 us while it requires 100 us to complete the conversion.

Result: Not a workable idea

Solution: Increase the I/O of microcontroller and use the software to generate the signals for ADC0809.

BTW: If you are so short of port pins, how will you feed the multiplexer the address information (even if your idea works)?

I am not sure, but think if ALE is driven by EOC signal so that this change happens only after the successful end of conversion.Even in that case, the question of how to provide address bits remains un-answered.