Buses leave from Quito’s Terminal Terrestre frequently, and take approximately 3 hours to get to Ibarra (the trip costs roughly $3). Ibarra is a common stop on the way to Otavalo, which is 45 minutes away.
Note that Ibarra does not have a centralized bus station – instead, each cooperative has its own office. The following are the bus cooperatives in Ibarra that operate between Otavalo, Quito and Tulcán:
Supertaxis Los Lagos (Flores 924 and Sánchez Cifuentes, Parque La Merced),
Trans Andina (Chica Narváez),
Expreso Turismo (Moncayo, between Flores and Vacas).
Trans Otavalo (Av. F. E. Vacas) also has an Ibarra location, but only operates between Otavalo and Quito.