Nearest airport is Jolly Grant airport (about 140 km). Taxis are available from the airport to Haldwani and Kathgodam. You have to break at one of these places and hire another taxi to reach Devalgarh.
Kotdwar (about 135 km away) and Rishikesh (about 120 km away) are the nearest railway stations. You can hail a cab from these rail heads to reach Devalgarh.