I've heard that the atmospheric pressure on venus is 90 times that of earth, but I don't know the melting point of $SiO_2$ at 90 atm nor at what temperature its vapor pressure hits 90 atm. Basically I'm wondering how ridiculous it would be to say that life on venus exists with a solvent of silicon dioxide.
All solid when under pressure have their melting point increase. The exception is water which decreases the point but then increases os pressure continues to increase; water is weird.
Silicon dioxide has a melting point of 1,986 K at 101 kilopascals (1 atmosphere).
Vesus' atmospheric pressure is 9200 kilopascals or about 91 times Earth's atmospheric, sea-level pressure. The mean surface temperature on Venus is only 737 K.
This is far below the melting point of silicon dioxide and with the increased pressure the melting point of silicon dioxide would be even higher.
So no, under normal surface conditions silicon dioxide would not be found in liquid form.
Venus and Earth have similar densities, so probably similar geology. Earth's crust is mostly silicon dioxide at around 40%. Assuming Vensus has a similar geology for its mantle, if your premise was true, the surface of Venus would be a ocean of liquid SiO2, as all the other major components would precipitate out or sink.
We have landed two probes successfully on Venus' surface and it looks rather dry and hostile. The probe didn't live long either.
Silica melts at 1705°C, at standard atmospheric pressure, as this phase diagram shows it's not until around 1GPa that there's much movement in that temperature, Venus with a temperature of 462°C and pressure of just 0.093GPa would have to be over 1200°C hotter before you saw liquid quartz on the surface. The pressure makes no real difference here, there's simply not enough of it to change the physical properties that are important to the problem. Silica as a biological solvent is an old, but still interesting idea, but there's no planet I know of where the temperatures make it a workable one.