You can still get good speakers, but your pool will be limited. One of the best ways to find good speakers is to ask your peers for recommendations. The best time to hold your conference is when your attendees are most likely to attend. Some conferences are best held during a slow time in the industry. Pick a location attendees will want to visit.
Location is a key factor for several reasons.
Transportation costs and hotel room rates can affect attendance. Knowing your target audience is the key. Second is providing a quality product that your audience needs and wants and is willing to pay for. Third, you must market your conference effectively. Finally, you need to stay within your budget.