score:2
Being there certainly would increase your chances - as you can go and see the places, meet the estate agents, and call people during day hours. Example: place comes on the market at 9am, calls start at 10am, they could show someone through at lunch and by the time you wake up in the US, it's gone.
I was in Riga in May sorting out my Uzbekistan visa, which took six days. There was a British woman in the hostel looking at places to live in. It was really hard, but with the help of locals (including the hostel staff) she was finding more sources, friends of friends who knew of places, and the like. Definitely easier when you're in a city than from afar.
You could also consider CouchSurfing a bit when you arrive, or do what I'll be doing for Vancouver when I head there soon, and stay in a hostel for a bit. There are some hostels in Riga (Central Hostel was really nice and good value) which aren't party hostels, but are very well located, and you'll make a lot of connections if you talk to the staff. Even going to a Couchsurfing meetup in town could net you some more connections or offers of a place to stay.
My recommendation - try from where you are, but accept that it'll be easier on the ground, and make back-up plans to make connections on your arrival.