Here are some suggestions for optimizing rendering times:

• Use internal lights on the fluid instead of a Maya light, especially if you have a lot of lights, or you are using expensive light types (like area lights). To use an internal light, turn Real Lights off in the Lighting section of the fluidShape Attribute Editor.
• Lower the Quality setting as needed to speed up preview renders.

  In general, lower the Quality until you see dotty artifacts, especially along the fluid edges, then increase it a bit. You can then try increasing the Contrast Tolerance. A low adaptive tolerance is useful when you have a fluid with sudden boundaries. Both Quality and Contrast Tolerance affect the shadow quality.

• Raytracing with Receive Shadows turned on in the Render Stats section of the fluidShape Attribute Editor can increase rendering time.
• Avoid the Billow Texture Type. Use Perlin Noise instead, with Inflection turned on.
• Try using the Shading Samples Override attribute in the Render Stats section of the Attribute Editor of the fluid. This may work well when you have a soft edged fluid (a hard edge will need anti aliasing). The fluid might look acceptable with Shading Samples and Max Shading Samples both set to 1. In some cases, this could half the render time.