Location: The Weizmann Institute of Science resides in a very nice campus, located at the northen entry to the city of Rehovot, which is located about 25Km (15 miles) from Tel-Aviv, 55Km from Jerusalem, and 15Km from Israel's main international airport (Ben-Gurion).
Getting there: A taxi from Ben-Gurion airport to Weizmann Institute should cost 125-140NIS (approximately 40USD), and I advise it. Other options seem a real pain, but details about them and about other things are available HERE.
The Lopatie conference center is located on the main road of Wezmann Institute (called Marcus Sieff Blvd); see Nr 2 on the campus map. San Martin / Maison de France Guesthouse appears as Nr. 45.
Food: The Lopatie center has a cafe/restaurant (and there are a few additional eateries on campus), but I prefer three places that are outside the campus at a distance of 50-100 meters from the main gate: Just cross Herzel street and Derech Yavne and you will see Vinona (a cafe at the corner), Ha-Nasich (a middle-eastern place next to it). A few additional houses to the same direction (south), there is another cafe (Emelia).
For a night drink, you may try one (or more) of several pubs at the area next to the train station, which is 5-10 minutes walk from the main gate. (But, of course, the real action is in Tel-Aviv.)
Tel-Aviv (TLV) prides itself of being a small New York (NYC). I think the claim is justified in the sense that you will like TLV if and only if you like NYC. I happen to love both.
The simplest way to get to TLV is to take a taxi. The cost should be 140-150NIS (depending on timing), and if you share it among 3-4 riders this seems comparable to other alternatives (e.g., train) in cost, but far faster... Weizmann Institute uses Rehovot Taxis (08) 936 3333. Other taxi companies are listed here.
A few of the popular outing areas in TLV include
To the web-page of the Weizmann Institute of Science, the web-page of TOC at WIS page, and to Oded Goldreich's homepage.