Yes, whatever you set in DEFINE ADC_CLOCK n, where 'n' is a number between 0 and 7 will reflect in bits ADCS2:ADCS1:ADCS0 as per the table in the PICs DATASHEET that I refered you to..

If you set a number greater than 7, then only the lowest three bits of your define will be used... ie DEFINE ADC_CLOCK 8 will set ADCS2=0,ADCS1=0 and ADCS0=0.

I will add, that if you don't specify a DEFINE ADC_CLOCK in your program, the default value if you use ADCIN will be 3 (ie ADCS2=0, ADCS1=1, ADCS0=1).