Yes - solar panels work more efficiently in cooler weather although they are designed to withstand the harshest summer conditions.  High (altitude) desert regions are optimal.

Ideally, the solar panels should be mounted on a roof, building or piece of land, where the panels have maximum amount of unobstructed sunlight.  This is typically on a tilted, south facing surface where the solar panel is perpendicular to sunlight.

It will typically take 1-3 days to fully prepare a site and install the system.

The size of the system depends on individual household energy usage, and whether you want to completely replace the local utility with a solar PV system.  Here is a quick way of assessing your system size:

Total up your kilowatt (kWh) usage for a year (see your utility bill).  For a small single family home the number would be approximately 4,000 kWh (annual usage)
Divide by the number of days in the year (365): 4,000/365 = 10.95 kWh (average daily usage)
Divide by the number of daily average sun hours for your location (5.5 in sunny locations): 10.95/5.5 = 2 kW (system requirement)
At $9.00 per watt installed the raw cost of the system would be $18,000 assuming no rebates or other incentives