From the East Coast, total travel time is roughly 24 hours.
You should plan to arrive in-country on September 12. This will leave time for delays as well as acclimating to the time change.
This question has multiple parts so check the questions below:
The local currency is riel with an exchange rate of 1=4,000 but dollars are used for everything that costs more than 4000 riel. Expect to use dollars for most transactions.
Most hotels and foreigner restaurants take Visa. *****If you have a chip on your Visa, call your credit card company to set the PIN***** *****Check to see if your card has international transaction fees.***** *****Bring 2 Visa Cards in case something happens to one. You will not be able to get a replacement quickly enough for it to matter***** Many merchants require you to enter a PIN to complete credit transaction. So, if you have no PIN, you will be unable to use the card.
***All ATMs will have fees. Check to see your ATM card for international fees as well. Some cards will refund those, some will not*** The ATMs all dispense US dollars. HOWEVER - they tend to give you large denominations such as 50s and 100s which are more or less useless. Occasionally, you will get 20s but they are not so useful either. Most denominations large than $5 are difficult to spend outside of hotels and foreigner restaurants. Most taxis and local restaurants tend to cost 1 - 5 dollars and they generally will not have enough cash on-hand (or won't care to) to give you change. ****The most useful denomination is single dollar bills*** Recommend 20 dollars per day in singles and another 20 dollars per day in 5s.
For the wedding days, there will be shuttles from the hotel and back.
Tuk Tuks are the most common form of taxi. Expect to negotiate the price a bit. Grab Taxi and PassApp are the two biggest App-based taxis. You can register and user your Visa card with Grab but Pass will require cash. Pass App seems to be a bit cheaper but you may find paying via CC on Grab easier.
Grab bought all of Uber's SEA business last year so there is no Uber. Use Grab instead.
Motorbikes can be rented from your hotel or a local rental. If you rent from a local place, you may have to leave your passport as the deposit. This is not that unusual but it is up to your comfort level. There are options that do not require leaving your passport so always prefer those. ****No local license required**** ****Bring your own helmet. Seriously.**** Cost depends on models. 125cc is generally $5 / day, $25 / week, $100 / mo. You will not need anything bigger than 125cc to get around the city. Some sites: https://www.emcmotorbikerental.com/en/welcome/ https://cambodiaexpatsonline.com/cars-motorcycles-motos/scooter-rentals-phnom-penh-t17611.html
You can get travel medical insurance / evacuation coverage fairly inexpensively. Generally, you will want a policy that will give you access to some care + a policy that pays for that care. E.g,, a policy that will give you access to medical evacuation should something happen then an additional policy that pays for that evacuation. Check with your insurance agent or AAA. Independence Blue Cross has an international coverage you can purchase. International SOS has the most coverage but will generally be the most expensive. International SOS has a clinic in Phnom Penh and you can buy coverage from them via their service or pay in cash onsite. Recommend the first option as pricing is close to US costs.
Check with your local travel medicine provider. In PA, Penn Travel Medicine is the best resource: https://www.pennmedicine.org/for-patients-and-visitors/find-a-program-or-service/travel-medicine