3:33 p.m. on January 23, 2013 (EST)
I have a Berikade Expedition it is pricy but it has gotten a lot of use (not all my own). A bit overkill for you now since you will probably not be going on more than 3 day trips that soon. It fits in either my or my wife's pack and doubles for stuffing other things in there when not full of food - or as it empties. I take the Berikade everywhere - it is just part of the kit now, bears or no bears, Rockies, Cascades, or desert. Foot stool, camp chair, bathing basin, stuff stuffer.
.https://www.wild-ideas.net/).
The Garcia is good for a single person for several days, but is heavier per cubic inch of storage and does not efficiently lend it self to good packing (restricted opening). You can rent them from where you pick up your wilderness permits (check to make sure).
I use this for my maps and planning: Price is right...
http://mapper.acme.com/?ll=37.10694,-118.51210&z=14&t=T
20F down bag in the bottom with rolled/strapped pad (3/4 size Therma-Rest). Bear can in top section centered. Tent on one side of it with poles, clothes on other in stuff sack. Cook kit (Lexan cup (with cup measure etched on inside), spoon, Pocket Rocket or MSR wet fuel and .8 liter pot (with stove/cup inside) and lid, two small BICs) some place with a down vest stuffed where it can go. Nothing on the outside to throw the balance off.
REI and your local (or area) Sierra Club have an assortment of trips planned through the year. Pick the kind of trip you want to join up with. Also there are hiking/backpacking connections on the internet such as
http://www.meetup.com/
In the Sierra you will seldom be 'alone'. You will get the drift of that when you apply for a wilderness permit. Especially on the weekends you will be passed by and pass several hikers an hour. And you can meet friendly fellow trail hikers at established (has large bear boxes for food storage) camping areas.
But hiking alone, is, well, alone. Part of the fun being out there is to share the experience. Most small groups of 2-3 usually are happy to have along a person who has most of their gear, has some level of fitness and is willing to learn and get involved. If answering an ad on line, it is best to meet up with them in a neutral environment - restaurant for hamburgers, day hike or just some means to see if you too have any personality clashes. You will be spending a lot of time together under less than desirable (rain/cold/snow/dark/lost) and at times stressful (at least physical) adventures.
By mid June in the Sierra, there will still be snow cover above 11,000'. This means that there will be no 'trails', the passes will be an adventure, and some creek crossings might end up with a cold unexpected bath.
Sierra snow trips are a lot of fun starting around March. At even relatively lower altitudes, you will have around 4' of very dense snow (Sierra Concrete) to walk on, there will be low risk of avalanche and you will enjoy a scene that few have been treated to. The temps will seldom drop to far below 20F at night and get up to the 70's - at times. From the west you have trail heads that start lower, the crowds have been scared away and you have no problems with spending the night with water. A personal varmint canister is still required as the bears in the Sierra don't hibernate so long as there is food available. The most damage I have had over the years has been from small rodents. Never a problem with bears - except for the routine precautions.
For backpacking you need to plan on mosquitoes (DEET used sparingly and often). A hooded jacket (Precip or better) over 200 (equivalent) fleece will do you for cool evenings and mornings and with thick socks will keep the skeeters at bay while eating or getting ready to go. The jacket and fleece provide for a lot of your 'layering' options too. There are insect nets that go over a brimmed hat (needed for sun at altitude) and weigh an ounce. With hi value UV protection, sun glasses and UV lip protection you are good to go for much of the Sierra.
Pick up a copy of Mountaineering:Freedom of the Hills. It is the guide to Backpacking 101 and is a good read anytime. Just pick a chapter you are interested in.
http://forums.backpacker.com/cgi-bin/forums/ikonboard.cgi
http://www.highsierratopix.com/community/viewforum.php?f=1
Are a few links (There are MANY) that 'specialize' in the Sierra or at least have a forum that answers questions for and provides a way to link up with others of the same intentions.
Unfortunately the Eastern Sierra is a long drive for you. It is a different Sierra experience than is the western approach (e.g., Yosemite Valley, Sequoia, Kings Canyon, Mineral King) and the longer trails to get to the spectacular views of high altitude mountains. The eastern side generally have trails starting near 10,000' so a lot of the effort to get up high has been taken over by your car. Instead of 15+ miles to a 11,000 pass it is about 8 miles. The way the Sierra were formed was an up lift of a large plate sloping down to the west and the eastern side 'broken' off forming a very steep 'back bone' - the High Sierra and most of the 14,000+' mountains in California.
Once you get a backpacking 'buddy' you can share some weight such as a tent and cooking gear. Usually even though you might be going with a group, most expect you to be 'solo' with your own tent, kit and food. Unless agreed to and planned for ahead of time.
Except for boots you might be able to test out packs and tents as a rental especially if you are near a REI. Also with planned groups you can have a show and tell about gear and get to see a few of the MANY options for everything.
Happy to have you join us when we are out there if times and places match up.