Go by the water tests as the most reliable, second go by the fish's behavior.
If you start doing too frequent of changes the levels may not reach the "tipping" point at which the beneficial bacteria can start to really flourish.
FYI, guppies are not the best choice for cycling. Keep a close eye on their gills and fins.
gills for any redness/inflammation, fins for any ragged, tattered edges, both signs of high ammonia levels (guppies are especially susceptible to fin deterioration) and labored breathing.
Test daily and do partial changes as needed, when ammonia hits >4ppm, nitrite when it hits about >0.50 ppm
, or if the fish appear distressed.
Also during the cycling period DO NOT clean your filters, it's actually counter productive when establishing a bacteria colony.
If there is obvious uneaten food/detritus on the bottom, siphon it out, otherwise it really doesn't matter at this stage of your tank.