You can exchange your dollars to BTCs online. There are middleman services that could help you. It's always better to keep our money in Bitcoins, as we are growing our money along the time as the Bitcoin price is constantly increasing, that is one of the aspects I like about Bitcoin. Our money isn't idle, it's always growing just by holding it in BTCs!
Unfortunately it is not that easy. Payments are not the problem, the problem is getting the money out of cash-based middleman. Either you have to transfer it to your bank account first and buy btc or use their debit card(if available) to buy directly(I dont even know if they allow this though). Basically you have to wait wait wait until you get your money.
If payments were made in bitcoin then none of this would happen and I would be happily doing what i do with a clean state of mind
. Let me also give you an example, I used many different online payment services like Paypal, Webmoney... Back in the day I deposited some money into Pokerstars... Everyhing is fine and dandy and one day Pokerstars decides to not operate in this country. They told me to use one of those services to withdraw my money. I used webmoney for this. Money came to webmoney but never to me. Little i knew that I had to send my passport copy by mail to get confirmed for withdraws. Some russian law. That I have a problem with. I deposited this money out of my credit card succesfully, Pokerstars verifed this, I gambled with it for a long time and one day they had to transfer this money to webmoney(big company transfering money so it can't be fraud right) but i can't withdraw this money because I need to be verified by this russian company by sending a passport copy...