What's the purpose of this capacitor?
The block on the right looks like it might need a dc bias on the RF input to make it work. This dc bias ultimately comes from the VCX pin via FB (ferrite bead) and the first decoupling capacitor then thru a 10 ohm resistor and the 2nd decoupler that you have highlighted.

Given the frequencies you are using (and my suspicion that it's a decoupler) then anything from 100 pf to 10n is probably going to work but, for the higher end of the range check that the self resonant frequency of the capacitor isn't so low that it might cause a resonance problem at 1590 MHz.