Small quantities of dissolved polymers impart elasticity to a fluid and are a crucial means to control the transition to turbulent flow, in various applications that range widely across Reynolds number. We measure flow and pressure macroscopically and analyze birefringence and particle tracking with high-speed imaging to obtain local flow and stress. We seek to measure features associated with the transition to turbulence, including wave propagation of flow disturbance, while adjusting the relative importance of elasticity and inertia by channel geometry.