The diarist Alf Doten and his companions from Plymouth, Massachusetts left home on March 18, 1849 and traveled around the horn, arriving in San Francisco on October 2, 1849, a voyage of nearly 7 months. The Grosh Brothers and their companions left Philadelphia on February 28, 1849. They sailed to the midpoint of the Mexico, hiked overland and picked up another vessel to sail up to San Francisco, arriving on August 30, 1849, a journey of nearly 6 months. In both cases, there were casualties, and the trips were by no means easy.

Some '49ers sailed to the isthmus linking North and South America, crossed overland, and caught a ship going north. That journey would take 5 to 6 months depending on the success of the connections.

Each of these three options were preferable for most in 1849 because the overland journey took so long and was so dangerous. While 1849 is not your question, it is worthwhile to consider the information we have because the sailing options would not have changed much from 1849 to 1870, so that's something of a benchmark.

By 1861, with much of the North American continent made more accessible, it was easier to conceive of a journey overland (although some 49ers had attempted it a dozen years earlier). Orion and Samuel Clemens traveled by stage from St. Joseph, Missouri to Carson City, Nevada in the summer of 1861, traveling for 19 days. For your traveler to start in New York and reach St. Joseph, we can add another week or so, but it would have been easy enough with rail connections. To travel from Carson City to San Francisco, we would need to add another few days. In all, the trip from New York to San Francisco could be accomplished overland in about a month, which was significantly quicker than the sailing options. The speed and safety of the overland trip started to increase after the Civil War. Then in 1869, of course, the transcontinental railroad changed everything.

I hope that helps.