The "best place" question is based on where you live and what insurance you have.
If you are insured, CVS is usually but not always the best place to get it from the standpoint that they are the largest pharmacy in the US so usually get it the fastest. If you are insured, any preferred pharmacy will be the same price.
For off insurance rates, I have found Wegmans of all places to be the cheapest (you have to ask for their discount plan), so I go to CVS for covered drugs and Wegmans for drugs not covered by insurance (like finesteride).
Injectables are in general something that needs to be ordered and take a few days. Estradiol Valerate generic does have a history of supply shortage, in which case delestrogen is the name brand and readily available. The difference in cost if you are insured is pretty staggering. I have Caremark and they did not want to cover delestrogen but after some badgering did cover me at the generic rate due to the supply issues.
Estradiol Valerate generic is currently available, and my last refill two weeks ago took the pharmacy 2-3 days to get in the store. Sometimes it's next day, once in a while it's longer. If you are on auto fill they will have it ready when it's time to refill.