Took the public bus from Arequipa (it left from near the intersection of Avenida Jésus & Cayro, NOT from Sepulveda & Espinar, & at 6:30am, not 7am) to Para (a junction before the town of Ubinas in front of the volcano). Hiked a bit, then waited several hours for the activity (LOTS of smoke) to die down before summiting in time for a spectacular sunset. I went straight up a steep ridge on the south side of the volcano to the crater rim, then hiked around to the left to the summit. Descended, then camped in a large flat area at 4,700m & caught the bus back to Arequipa the following morning, it passes the junction around 9:30am.
Arrived at the mountain in the evening so was a little hard to find the right roads and the base camp. We camped low at about 15,100', summited the next day, about 7 1/2 hours round trip. Just a little smoke and some sulfer fumes, with a long hike/climb around the rim to the summit.
Climbed successfully but chased off the summit several times. Once by funes spewing from the crater and then lighting. Made summit betweeen storms and spurts of fumes from the crater. A true adventure, Ubinas is doable but do not camp on mountain. Daily buses go from arequipa and Ubinus by the base of mountain.